Geotrail Biševo


You have set your foot on the island of Biševo in the Vis archipelago. Biševo boasts two monuments of nature. The Blue Cave is the most attractive monument of nature in the archipelago, featuring a unique effect produced by sunrays in the cave interior that simply leaves you breathless. The other monument of nature, the Monk Seal Cave, is only a mile away. It is the longest semi-submerged cave in the Adriatic, with the total length of 160 meters. As its name implies, this cave used to be a hiding and breeding ground for the Mediterranean monk seal species, which reared their young on a small pebble beach at the end of the cave hall.

This trail describes the geological origin of the island of Biševo, as well as the cultural and natural heritage of the inhabitants of this beautiful, exotic island.

In the Mesozoic or The Age of Dinosaurs and the beginning of the Cenozoic or the Age of Mammals, Biševo was located in a tropical belt in the middle of an ancient Thetis ocean. Biševo was a part of a small continent located between Europe and Africa called the Adriatic Carbonate Platform, which was covered by shallow and warm sea teeming with life and numerous organisms. Biševo’s sedimentary layers were built from numerous shells and remains of these organisms.When the Adriatic Carbonate Platform collided with Europe, these sediments were tectonically elevated, resulting in the formation of the Dinaric mountains and the present day islands of the Vis archipelago. The Quarternary period, when the sea level was as 140 meters lower than today, was marked by dry and cold Ice Age. Strong winds carried the sand from the steppes to the surrounding hills, present day islands, and it is for this reason that Biševo has beautiful sand beaches and fertile soil which yields the finest quality grape.


The Viennese painter Eugen baron Ranssonet, discovered the Blue Cave on the island of Biševo. In the Viennese daily Neue Freie Presse, on Thursday, August 7th 1884, no. 7165, an article by Baron Eugen Ransonnet was published: Die blaue Grotte der Insel Busi. This article sparked a massive interest of the Austrian public for the natural beauty of the coast and islands of the Austro-Hungarian Empire. It was a sensational news story about the discovery of the natural Adriatic phenomenon - The Blue Cave on the island of Biševo, whose beauty, as Ransonnet believed, tops the more famous Grotta Azzurra on the island of Capri which was then considered the most beautiful sea cave in the world.

As we leave behind a bright summer day and enter the dark tunnel of Biševo’s Grod Balon cliff, we soon encounter that deep blue beauty which flashes at us from the sea, that colour which turns all objects and bodies immersed in it into liquid silver. And we know with certainty that we are in a mythical place, that we have crossed over from reality to a supernatural realm, on a small boat, and into some unexplicable mythical ambient of a sea deity which fills us with never before encountered feelings and miraculous strength. We know with certainty that we will come out of this temple of beauty as different people than the ones we were before the entrance.


The youngest layers from the stone "book" of the island of Biševo are Paleogene limestones formed during the Age of Mammals. Like small pieces of rocks tumbling down a snowy slope, these balls were formed by the sliding of the sediment of biogenic material down the slope of the sea bottom, where they formed nodular ("ball-like") textures.

ThePaleogene limestones built the central part of the island of Biševo, and could be discerned by the harsh (rough) surface and nodular (wavy) layers. They are easily decomposed into calcareous sand which was carried by the wind to the sandy plains and the valleys during the last Ice Age. Sand was formed of the millions of tiny calcareous testsof protozoa (foraminifera), algae, sea urchins, shells and their debris. The accumulated grains of sand in the sediment are subsequently cementedinto a solid rock - limestone.


Approximately 100-120 million years ago, some land plants became underwater plants again. One of such plants is also the Posidonia oceanica, an aquatic plant bearing flowers and fruits whose exclusive habitat is the Mediterranean Sea. The posidonia seagreass species is also the most widespread endemic seagrass of the Mediterranean. It was named by the famous Swedish botanicist Linné, after the Greek sea god Poseidon.

Posidonia plays an important role in the ecosystem of coastal areas in multiple ways. In posidonia meadows there are as many as 400 various types of plants and a couple of thousand animal species. Only upon careful inspection we notice that the seemingly empty posidonia meadows are actually teeming with life and are densely populated habitats of marine life. On posidonia’s leaves a plentitude of plant and animal species flourish. We call these organisms epiphytes (from the Greek wordsepimeaning "on" andphytonmeaning "plant"), and they are a food source to fish, mollusks and crustaceans. Due to their elongated leaves and a developed network of rhizomes, the posidonia catches sediment particles, adding to the sea’s transparency. In the autumnal period, the posidonia seagrass, also known as "lažina" in Dalmatia, protects Biševo’s sandy beaches from sand erosion. It has been estimated that the island of Biševo is surrounded by 200 hectars of posidonia, which together with sea caves, corallogenic reefs, sand beaches and the submarine world, make up the area called “The Biševo Sea” within the ecological network Natura 2000. Just like continental forests, posidonia meadows represent the "climax" community (i.e. the final stage in the long ecological succession) in the coastal submarine area, which produces significant amounts of oxygen crucial to life. Due to its slow growth, between 1 and 7 cm on average per year, posidonia meadows take a long time to become restored. It is therefore of exceptional importance to take all preventive measures to protect posidonia, by regulating the negative human impact – constructing the necessary sewage systems, prohibiting the filling of coastal areas, prohibiting usage of driftnets as fishing tools, and the regulation of anchoring.

The Mezuporat Bay on Biševo has an ecological mooring system. The boats are tied to the floating buoys, so as to avoid the repetitive anchoring to the seabed where the sensitive posidonia meadows are located. Throughout history posidonia was usedas fertilizer, material for the covering of roofs and the construction of resting mats. In the Lazaret cave in Nice, the remains of a bed made from posidonia were found, which people have used from 10 000 years ago.


In the hinterland of the Blue Cave the consequences of the violent dynamics of the Earth's crust can be seen. Due to the action of tectonic forces and the slow movement of large blocks of the upper parts of the crust, the rocks became fractures resulting in the blocks moving along these fractures – flat surfaces known as the faults. Traces of tectonic movement or scraping of the Blue Cave’s block against the central mass of rocks on Biševo, can be seen along the sleek fault plane called paraclasis. This fault intersects the rock so it can be traced from the southern entrance to the Blue Cave to the northern, narrow passage between the shore and a small islet along which the boats with the Blue Cave visitors are sailing.

The Blue Cave was probably formed through selective erosion (abrasion),during the interaction of tectonic (diapiric) rise of the island and rises of the sea-level after the last Ice Age. Namely, the rocksof the terrestrial phase are softer than the surrounding carbonate rock, and that very horizon (a ‘page’) from the stone "book" is presumably located in the level of the submerged parts of the Blue Cave. Waves propelled by strong southern winds crashed into and washed against the softer rocks, carving our a large hole in them – the present day Blue Cave. Erosion is faster along the intersection of the cracks in the rocks and the holes are still forming along the cliffs.


People have been exploting rocks since prehistoric times. On the island of Biševo there are various types of limestones which occur naturally in various forms - as massive, thickly bedded, nodular (wavy), and platy. This natural material was hence used for construction of houses and other objects on the island.

On the island of Biševo’s flatlandsthere is a spacious plain (Poje, meaning field in Croatian) with the largest homonymous settlement in this picturesque countryside. The Church of Saint Sylvester is the largest building on the island, and is made of various types of carefully selected Biševo limestone (carved blocks, boulders and plates). The second largest building on the island is the former elementary school, the site of the future visitor info centre. This building was also constructed from the local Biševo limestone, as are most of the other objects on the island.

The people of Biševo used various types of geological substrate for a variety of crops, whose fruits allowed life on this remote island. Because of specific geological conditions, the highest quality soil on the islands developed in the area surrounding Poje. A lovely view of the island of Svetac stretches from this plain. Springtime ushers in true Mediterranean heaven here, when the macchia bush blossoms into a spectacular floral oasis.


In 1050 a priest from Split by the name of Ivan erected a church on Biševo’s plateau and consecrated it to Pope St. Sylvester (314 – 335), who was the first in the history of Christianity to secure Christians’ rights to publicly declare their faith. Father Ivan gave the church over to the Benedictines from the Tremiti islands. St. Sylvester’s Church was built in Pre-Romanic style, but its original configuration was changed over the subsequent centuries. Benedictines arrived to Biševo at that period and erected their monastery in the vicinity of the church.

In the tumultuous period of battles between Venice and Byzantium over rule of these areas, the monastery of St. Sylvester on Biševo turned to Pope Alexander III for protection. On May 2th, 1181, the Pope signed a privilege under which he placed this monastery. The letter begins with the Pope’s address to the monastery’s superior, abbot Urso: „Alexander the Bishop, servant of God’s servants, to his dearest son Urso, abbot of St. Sylvester’s monastery on the island of Biševo and his monastic brethren, the present and future ones, for all times.“

One of the oldest paintings of Madonna in Croatia, the work of the proto-Venetian painting style from the 13th century (dated 1220), was preserved in this church on Biševo – Madonna from Biševo was believed to have miraculous powers.


In 1921 the first school on Biševo was founded in a private family home in the village of Porat. The primary school educated children in grades 1-4. In 1937 the inhabitants of Biševo built their own school building in the village Poje. The school was actively working until 1961, when it had to be shut down due to a small number of school children. Before World War 2, Biševo had 350 inhabitants, in comparison to the 2011 population census which registered only 11 permanent residents on the island. Many of its former residents have permanently emigrated to the United States, mainly San Pedro in California or to Australia.

A pupil’s notebook from 1956 was found in this building. In it was an essay on the subject of their native island:

Biševo, February 14th, 1956. Fifth school essay

My village

“My village is called Biševo, it is in the middle of the Adriatic. People here are farmers and fishermen. My village is surrounded with hills and a small forest. The houses are scattered around and people say it’s quite desolate. My village has no railroads and power stations, no movies or theatres. We don’t get the big steamboats as in the big cities. My village is small and it has one world famous cave.”

These words were written down by a little boy named Petar on a cold winter morning of 1956. A third-grader, Peter wrote about his island in the middle of the Adriatic, known for its Blue Cave.

In 1990 the town of Komiža in association with the University of Zagreb, initiated the project of restoration of the Biševo school building, with the idea it would eventually house an international research centre.This happened around the time when the island of Vis and its archipelago came out of isolation after 45 years of being a military zone, bringing the first foreign tourists to the island. Everyone hoped that they might use this historically unique moment to start a sustainable development programme on this desolate archipelago. This project was stunted by the onset of the Homeland War but the idea remained alive, only to be realized 28 years later, when the Biševo school building will undergo renovation that will transform it into a new Interpretation Centre on Biševo.


At the end of the Age of Dinosaurs, at the end of the Cretaceous, the wider area of the island of Vis emerged on the surface. Once exposed on the surface, the limestone rocks slowly became subject to the new, terrestrial conditions. Much like present day "muddy" rains which contain desert dust from the Sahara, back in the day the openings in the paleokarst were filled with the reddish-brown dust. Today we can find this dust in the form of reddish-brown petrified soil.

Acting as a type of time capsule, the ground has preserved animal bones as a memorial of the time when, instead of present-day islands of the Vis archipelago, there was once here a large island in the middle of the Tethys Ocean. The islanders were dinosaurs, crocodiles and other land animals.

The sea life flourished again after the sea flooded this area again during the Paleogene period. During this period an entirely different type of limestone rocks were deposited. Unlike limestone rocks of the Cretaceous period, these took on the form of biogenic limestones, not the reddish-brown but light-brown in colour.


In the youngest geological period – Quaternary, you would not be able to come to Biševo by boat, but with a jeep. During the Ice Age of that period the climate was dry and cold and the sea level was 140 meters lower than today. Instead of the seabed, the Adriatic steppe was the landscape that surrounded us, and the islands were scattered peaks of the hills. The steppe landscape was dominated by sand which the winds scattered over the surrounding hills. Present-day sand fields are just erosive remnants of these larger sandstone roofs. Such specific soil has enabled the cultivation of high quality grapevines and has become home to numerous populations of land snails. Most of the sand was partly washed by rains into the valleys that were submerged by the sea after the last Ice Age. For this reason we can find on this island some of the most beautiful sandy beaches of the archipelago: Porat and Sarbunora.


He was born on the island of Biševo in 1893. Before doing his few years of military service in the Austro-Hungarian army, he decided to go to the USA in 1913. He boarded the steamboat Martha Washington in Trieste and, after an eighteen-day journey, disembarked in New York without knowing a word of English and carrying only $22 in his pocket, but he possessed enormous fishing experience gained from fishing with his father in his early youth. He arrived in Astoria, in Oregon state. Hearing that there were fishermen from Komiža in Tacoma, he set off in search of fishing work. It was a pioneering time of fishing in Alaska, when fishing was still powered by sail and oar. They went terrible conditions for salmon fishing.

Pavao Martinis went down in the history of American fishing not only because of the record catches of salmon in Bristol Bay and the Bering Sea, but also as the first American fisherman who discovered salmon in the rich and dangerous waters of the Aleutian Islands. America acknowledged him officially for his fishing endeavours by awarding him the title King of Salmon, given to him by the president of the USA Dwight D. Eisenhower in 1956.


Sarbunora, one of the three coves on Biševo, was named after the Komiža expression for sand – “sarbun”. On the north-western edge of the island the whole epoch of the Earth’s crust emerged from the sea depths in the form of the “books”. Collision of the Adriatic Carbonate Platform and Europe has resulted in a tectonic rise which shaped the Dinaric mountains and these hills, present-day islands of the Vis archipelago. Spectacular cliffs we find all along the coasts of these islands tell us of this exciting geological event. Every ‘page’ of this geological book tells us a thousand year old story. The rich records of “Poseidon’s Library” are found all along the Salbunora Bay, andare decorated with fossilized ornaments that depict the contours and textures of prehistoric life. Carbonate sludge and sand, later tempered (litified) into a layer of solid limestone rock, formed from chiseled parts of fossil shells.

In the lagoons of the Adriatic Carbonate Platform, buried in sludge, at the bottom of the warm tropical sea, many of the former shellfish were inhabited by rudists. The asteroid impact 66 million years ago sealed the fate of these prairies and all of their life forms, includingdinosaurs. In the period of the rising sea level, crusts from shellfish rudists and snails were crushed into fine sand and swirled around by sea currents, which createdsand bars.


The story of this important man from the island of Biševo, which was passed down by word of mouth, tells us how, one day, Martin was busy tilling his vineyard and in the process broke the handle of the hoe. He was in a dilemma whether to fix it or simply go to America. He opted for America after all. He had just finished his naval service in the Austro-Hungarian Navy and was free to leave his homeland.

In San Diego he became a fisherman. When he increased his income from fish trading, he decided, in 1917, to open his own factory. But to enable deep sea fishing, far away from the shore, it was necessary to preserve the fish on the boat. In the book entitled The Port of Los Angeles it is stated that Martin Bogdanović was considered to be the innovator who first used crushed ice to preserve fish. The door to the vastness of the Pacific was open.The strength of his cannery was based on the exceptional capabilities and experiences of the people from his homeland. Martin Bogdanović came from a poor country into a land which offered opportunity to the competent and the courageous, and so, the poor fisherman from the island of Biševo became the greatest name in American fishing history.


The coasts of the island boast a number of interesting geological forms, extinct molluscs from the Age of Dinosaurs, as well as lithified sandbanks built of millions of ammonites. The Salbunara sands are home to the rare and endangered species, the sea daffodil (Pancratium maritimum), which is not to be picked. The upper Salbunara sands are home to an abundant snail community and sand vegetation with the stenoendemic species, the woodruff (Asperula staliana), that can be found only on Biševo island. It is accompanied by the prickly dropseed (Sporobolus pungens), the critically endangered cogon grass (Imperata cylindrica) and the rock rose (Helianthemum jonium), only recently discovered in Croatia.


Big wildfire of 2003 that engulfed more than three-quarters of the island had a major impact on the forming of the current vegetation cover of Biševo. Only the northernmost part of the island was spared. Thus, the island is currently dominated by the rosemary (Rosmarinus officinalis) and the Mediterranean Heather (Erica multiflora) garrigue. Before the fire, the south part of the island was covered in the natural Mediterranean evergreen forest of the holy oak (Quercus ilex). Today, only the forest of the Aleppo pine (Pinus halepensis) has grown on some locations. So far, a total of 485 plant species have been recorded in the terrestrial flora of Biševo island. The island boasts 43 plant species that belong to various categories of endangered species, 88 protected plant species and seven endemic species. Although to a lesser extent, Biševo vegetation is also represented by the cultivated scenery, mostly covered in vineyards, which once dominated the island.


The Mediterranean Sea and its bordering seas pose an obstacle for bird migration, so the birds use islands along the way, especially pelagic islands, to rest. Biševo is one of these islands. The best time of the year for bird watching on Biševo is autumn, because the autumn migrations are slower and the birds stay at way stations for a longer time. Nevertheless, one should bear in mind that different species migrate at different periods of the year, so the “autumn” begins already in the second half of July, lasting until mid-November. Thus, the autumn bird migration across Biševo and other pelagic islands over tens of thousands of years actually created an entirely new ecological niche, to which a new species, Eleonora’s falcon, adapted throughout the years of evolution. Read more about the Eleonora’s falcon on the panel number 25.


The composition and the shape of the grains of sand (predominantly grains of carbonate rocks, as well as extra small quantities of minerals from igneous rocks) together with their structure, show that these sands formed in the dry climate conditions. In addition, the fossils of the Quaternary land snails that lived in the arid and relatively cold climate some 25,000 years ago were found in the sands. At that time, the northern hemisphere was predominantly covered in ice and the level of the Adriatic Sea was some 120 m lower than today. Consequently, Biševo was only a hill in lowlands, influenced by big rivers Cetina and Neretva that carried material from the distant Dinarides. The wind carried such material, including the material formed by the erosion of small local islands built from igneous rocks, to hills such as Biševo.


Next to the villages there are vineyards and small areas of arable land covered in orchards and vegetable gardens. Fruit cultures grown on the island comprise vineyard peaches, nectarines, sour cherries, plums, olives and citrus fruit. There is a saying: “Praise all wine sorts, but cultivate plavac”. The autochthonous Croatian grape variety plavac mali is the most important variety of the central and south Dalmatia. As it is strong, it is often called “the wild wine”. Its special taste comes from the aeolian sand, the high-quality substrate it thrives on. The Plavac Mali wine is the first wine to receive the protected geographical indication in the Republic of Croatia. Due to its characteristics, the Biševo Plavac was a very popular wine on the European market in the end of 19th and the beginning of the 20th century. In that period, the outbreak of phylloxera (Dactulosphaira vitifoliae) struck Europe, destroying almost all European vineyards. Luckily, the phylloxera has difficulties developing in sandy soil, so vineyards of Biševo survived the European wine crisis.


Smokvina grotto, originally called “grotto of Gatula” got its name after a big fig tree growing from its opening. The diameter of the opening averages 7 m and the furthest and the deepest SW part of the grotto ends in the impassable narrowing, buried in deposits, suggesting that the grotto was even deeper in history. The second grotto on Gatula, Jezera, is located across the macadam road, some 50 m from Smokvina grotto. It has two entrances, the cave-type entrance and the grotto-type entrance. A few thin stalactites (called the macaroni pasta) are visible on the ceiling of the main cave hall, while following the creeps there are bigger speleothems – primarily calcite formations, stalagmites and stalactites. The 29 m deep Jezera grotto is the deepest grotto discovered on Biševo island so far. It belongs to the habitat type 8310, so the public is banned from visiting the grotto. Protected Chiroptera bats inhabit the grotto. It is the typical habitat (locus typicus) of the diplopoda class centipede (Eroonsoma Adriatica), first described in 2003.


A total of 74 artillery batteries existed along the eastern shore of the Adriatic Sea, with 31 located on the mainland and 43 on islands. The island with the largest number of batteries was Vis (7), followed by Korčula and Lošinj (4 each), then Veli and Mali Brijun, Cres, Žirje, Veli Drvenik, Hvar i Mljet (2 each). A battery is an artillery military unit consisting of artillery weapons. It consists of 50-60 soldiers and 3-6 artillery pieces. It can serve as an air defence, coastal artillery defence etc. There is a stationary artillery battery with four cannons at cape Gatula. Fortification objects are dug in beneath the surface. Masking of the open section of the gun position facilitated the camouflage of the battery into the environment. The illustration shows the sketch of the mines organised in a manner that allowed the soldiers to spend longer periods of time underground. The inventory of the Adriatic coastal artillery dating from 1948 states that the Biševo coastal artillery battery had four 80mm cannons of the Czech origin, of Škoda brand, with a total of 5088 pieces of ammunition.


Starting from 2007, the Blue World Institute carries out scientific research of the bottlenose dolphins in central Adriatic. Numerous schools of dolphins have been observed in the area ahead of you. Gaze at the sea and try finding a school of dolphins yourself! Several hundred individuals live in the wider Biševo area, so you may notice Kulfor, Napuhavac or Babalina, who owe their names to local terms for the species, as well as centuries-old co-existence of people and dolphins in the Vis archipelago. If you visit the island in the spring or early summer, you will get the chance to see the new dolphin calves swimming next to their mothers. Waters immediately surrounding the island and representing an important habitat for those animals have been declared a designated protected area under the Natura 2000 ecological network in order to ensure favourable conditions for the survival of the animal community.


The creation of the two most prominent caves, the Blue Cave and the Monk Seal Cave, is related to the tectonic processes that determined the orientation of the caves (the Blue Cave fault, the Biskup fault), while the erosion and corrosion processes expanded and shaped their passages. The creeps in the southern Trešjavac cove have also been formed by the tectonic processes, probably by rising of the salt diapir. In the north of Biševo, the elevated and sloping deposits of the former Adriatic Carbonate Platform form a stone book called Libar, which keeps records from the Age of Dinosaurs. Significant surfaces of the island are covered in thin, up to 10 m thick cover of aeolian sand, which has been deposited by the wind, as its name suggests (Aeolus, from Greek: Αἴολος, Aiolos, the Greek God of wind). The greatest deposits of aeolian sand are found in Salbunara and Potok.


Throughout the history, the seas of Biševo have been a source of food for the island’s inhabitants, while today they are the source of income for the entire community of the Town of Komiža. Should there been no Blue Cave as the most recognisable sea phenomenon of the entire story, there would have been neither the Visitor Centre nor the panel you are currently reading. The two most prominent semi-submerged sea caves, the Blue Cave and the Monk Seal Cave, are the most famous tourist attractions of the central Dalmatia. Nevertheless, Biševo waters hide even more valuable sea treasure. You can read about posidonia habitats on the panel no. 4 above the Mezoporat and about the aeolian sands of the beaches on the panel no. 15 at Salbunara beach, while the story about the deepest parts of Biševo, the coralligenous reefs named after the red algae of Corallinaceae family is kept for the top of Stražbenica. Those deep rocks are overgrown with corals such as the gold coral (Savalia savaglia) and the small polyped gorgonian (Paramuricea clavata), while the red coral (Corallium rubrum) lives in the greatest depths and in the hidden crevices. The shallower reefs in the tide level are covered in the algal pavements mainly constructed of the  Lithophyllum byssoides algae, which serves as an excellent indicator of the median sea level.


The only Mediterranean seal, known in the area as “morski covik”, is currently believed extinct in the Adriatic Sea. Today, the Mediterranean monk seal abides only in the NE Mediterranean Sea, the Cabo Blanco peninsula in West Sahara and the archipelago of Madeira. The monk seal was last seen on Biševo in 1964, when a fisherman killed it. The genetic research revealed it was an adult female. The northern, narrower and less passable section of the 160 m long Monk Seal Cave ends in a small pebble beach, ideal for the monk seal to raise their young. The entrance to the cave is impressive, featuring a big, ribbed fault plane (paraclasis), resembling huge, stone sliding doors, the so-called tectonic entrance, some 27 m high and 7 m wide.


Eleonora’s falcon (Falco eleonorae) primarily nests in the Mediterranean and the pelagic islands. The wider area of the Vis archipelago, including Biševo island, is one of such areas. The largest number of nests can be seen in the south of the island, surrounding the Trešjavac cove. There are two interesting facts pertaining to Eleonora’s falcon – its unusual preference for the pelagic islands and the time of its nesting – summer and early autumn. All other birds nest in the spring. Why is that so? The animal communities are synchronised and intertwined in a miraculous manner, with each species filling its niche. Thus, Eleonora’s falcon – a small bird of prey feeding on small birds – set its reproduction in the time and at the location of the highest concentration of small birds which they bring to their hatchlings – at the pelagic islands in the time of autumn migration. And then, when the young birds spread their wings in October and November, these falcons slowly head south, all the way to Madagascar, where they spend the winter.