Information Points
The Karst Edge information point

The Karst Edge information point

General information

There are three geographically and culturally diverse landscapes along the route of the Second Track: the Karst, the Brkini hills and the Coastal region of Slovenia. Three worlds, fascinating and unique, where, alongside natural and cultural sights, there are also unexplored areas, fragments of people’s lives and interesting stories being revealed. Discovering the Karst, Brkini hills and the Coastal region of Slovenia is a unique and unforgettable experience.

Opening hours: during the winter season: Saturday and Sunday from 10:00 AM to 3:00 PM.

Discover the landscapes and the towns along the Divača-Koper Second Track

Karst

The Karst is a world of underground caves, sinking rivers, sinkholes and dripstones. The Škocjan Caves near Divača are listed as a UNESCO World Heritage Site for their uniqueness. The Vilenica Cave is the oldest tourist cave in Europe, and the Divača Cave, the Dimnice Cave and the Križna Cave are also very interesting. The most famous and most visited cave remains Postojna Cave.

The Risnik collapse doline in Divača is also a Karst attraction. The Divača Karst Nature Trail runs around the collapse doline, bringing visitors to the Divača Cave.

Coastal region of Slovenia

The Coastal region of Slovenia, with its rural villages and towns along the coast, is located between the Karst Edge and the Adriatic Sea. The Mediterranean climate and generous soil, the authentic character of the nature, the people, the rich heritage, the varied cultural activities, the lively creativity and sporting activities are just some of the features of this part of Slovenia.

The route of the Second Track crosses the steep Karst Edge, with a height difference of 400 metres, and then descends towards the sea along a series of five tunnels and two viaducts all the way to Koper.

Karst Edge

The Karst Edge is the geological and climatic border between the Slovenian mainland and the Coastal region, where the Karst Plateau transitions into the flysch landscape of Istria. The Karst Edge also refers to the landscape where the Karst Plateau, with its steep, repeatedly tectonically broken edge, transitions into the flysch landscape of Istria. Also known as Breg or Bržanija, this landscape is a true geological, geomorphological and climate boundary.

The transition between the limestone plateau and flysch begins above Trieste already, although the real beginning of the Karst edge can be considered to be the Kluč pass near Katinara in the surrounding Trieste area. From here on is normaly where Istria begins, i.e. the Karst Edge winds from the previously mentioned pass to Socerb at the Slovenian-Italian border, from here it stretches in a strip of about 20 kilometres long and 2.5 to 5 kilometres wide all the way to Mlini at the Slovenian-Croatian border. In the course of the twentieth century, the part of the Karst Edge located in Italy became known as Breg, while the Slovenian part of the landscape is known simply as Karst Edge (Kraški rob) or Bržanija, although the name Breg is also used on this side of the border.

The geographically, geologically and climatically diverse world offers favourable conditions for a wide variety of flora to grow. The diverse Karst world, with its underground caves, abris and precipitous cliffs, and the entirely different, flysch Istria, attract many botanists, cavers and birdwatchers. As many as 1688 animal species have been identified here, including a large number of endangered ones. Alongside 28 endemic species, 10 species new to science have been discovered. The Karst Edge is intertwined with numerous cycling and hiking trails, and is also considered Slovenia’s main rock climbing area. More than half of all rock climbing routes in Slovenia are located here.

Socerb, Črni Kal, Osp, Gabrovica, Tinjan, Škofije, Plavje and Dekani are towns along the Second Track that are home to cultural monuments, characteristic architecture, excursion points and beautiful vistas, as well as local people dedicated to wine- and olive-growing.

Socerb

Socerb is best known for its castle (also known as the Strmec Castle), which stands on the edge of a 300-meter-high cliff at the northernmost part of the Karst Edge. Its extraordinary strategic position gave it great importance in the past. Mentioned as early as the Middle Ages, it was owned in the 14th century by the Ducain family of Venice. The castle has been damaged several times in a number of wars, and has also changed ownership continuously. The castle was also visited by Janez Vajkard Valvasor, who described it in his famous work The Glory of the Duchy of Carniola. About 300 metres from the castle is the entrance to the Holy Cave, 44 metres deep and 200 metres long. Legend has it that the young Saint Servulus (san Servolo) lived there as a hermit for two years after he converted to Christianity. He was executed for his faith by the Governor of Trieste in 283 or 284. The cave was converted into a sanctuary, and now houses the only underground church in Slovenia, where, up until the Second World War, a holy mass was celebrated every year on 24 May.

In the village of Socerb there are two village puddles. From Socerb, a mountain trail leads along the Karst Edge to Hrastovlje and Slavnik. Just outside Socerb is the hamlet of Kastelec with the Church of St. Helena.

Črni Kal, Gabrovica

Črni Kal is a village situated along the Koper-Ljubljana regional road, a village with a medieval layout and several buildings dating back to the 15th and 16th centuries. This Karst-Istrian village is home to many architectural gems, including the so-called Benko House dating from 1489, which is considered to be the oldest country house in the municipality of Koper. The house is also the oldest known marked and dated building of folk architecture in Slovenia, with traces of contemporary late Gothic and Romanesque design. The village is also recognisable by the bell tower of the Church of St. Valentine, which dates back to 1680 and has tilted by over a metre as a result of the subsidence of the terrain.

The history of Črni Kal is rich: remains from the Palaeolithic and Roman eras have been unearthed in a nearby quarry, and there are remains of the 11th-century castle (fortress) of San Sergio at the edge of the cliff, accessible via a metal footbridge.

The following places of interest in the village are worth a visit: the Črni Kal 17 homestead (with the remains of old homestead with a Karst courtyard (‘korta’) and a preserved, stonecut gate (‘porton’) bearing the inscription ‘A.V.47’). and the year 1863), the Črni Kal 37 homestead (dating back to 1818; the homestead consists of a residential building and outbuildings with rich stonemasonry details) and the Črni Kal 38 house (built between the 16th and the 18th centuries; a low, single-storey house with partially preserved typical features of the architecture practiced in the villages below the Karst Edge). Interestingly, the villagers utilised the favourable climate to plant various Mediterranean plants, the fruits of which they sold in the markets of the coastal towns and Trieste, and their wine even in Vienna.

Gabrovica is divided into the old and the new village. The old village (which was burnt down in May 1944) is situated just below a steep Karst hillside, and its origin is probably linked to its favourable location. About 100 metres to the south, Nova Gabrovica, a clustered settlement was built after World War II, and is now listed as a Settlement Heritage Site. There is a medieval church in the village – the Church of St. Nicholas – and you can also visit the watering place and the laundry sink (a well-preserved stone reservoir for drinking water; dated back to the turn of the 19th/20th century) and the old well from 1762.

Osp

Osp is a village to the north-west of Črni Kal, accessible via the village of Gabrovica. Osp is one of the oldest villages in Slovenia, first mentioned as early as in 1067. The compact village centre is interspersed with narrow streets (building blocks and enclosed courtyards), while the main street winds its way up to the Grad Cave, where the Osapska River springs. The cave is closed to visitors in order for bats to be able to raise their young undisturbed. There used to be a castle (fortress) outside the cave, and today you can see here the remains of the defence walls.

Osp is best known for its 200-metre-high wall above the village, which is an extremely popular rock-climbing area in Europe with 55 climbing routes. With its defence walls, Osp was in the past one of the most important defence posts against the Turks. There is also the 18th-century Church of St. Thomas and a water spring, which used to supply the locals with drinking water.

Tinjan

The village is situated on a hill close to the Italian border and is one of the most beautiful viewpoints of the Gulfs of Koper and Trieste. During the Iron Age, Tinjan was a fortified outpost, and during the Roman and medieval periods, here stood a defensive tower. According to certain sources, the name of the village goes back to Roman times. It is said that the warrior clan Attinium lived here. The legend continues that the other inhabitants resisted the clan, thus “acquiring” the name of Anti-Attinium, which resulted in the name Tinium, hence Tinjan. The remains of the defensive walls stand next to the Church of St. Michael. The church stands at the village edge, on a walled plateau of the prehistoric hillfort.

The Baroque-style, single-nave Church of St. Michael has a square shaped presbytery and a bell tower, and was built before 1700 on the site of an older church from the 13th century. The church’s main altar is made of grey and red marble. On the outer wall of the sacristy is an ancient stone head, probably from Roman times. There is a bronze statue of the Roman god Mercury, patron of merchants, dating from the 2nd century, which was found here and is now kept in the National Museum in Ljubljana. Tinjan is the last hill on the Slovenian mountain trail before it ultimately descends to the sea.

Construction methods of viaducts

Viaducts are crucial and fascinating achievements in civil engineering, which make it possible to bridge valleys, rivers, roads or railway lines at high altitudes. There are several different methods of viaduct construction, which are used depending on the type of terrain, the material resources and the requirements of the project. Within the Second Track project, three viaducts have been constructed using three construction methods.

Glinščica Viaduct – monolithic construction

The monolithic concrete viaduct construction is a method of viaduct construction which involves the use of a single continuous concrete casting, creating a strong and homogeneous structure. This technique involves the laying of formwork and reinforcement, and then casting the concrete, all in one single process. This allows for quick construction of large sections of the structure at lower heights with fewer joints, which can reduce costs and construction time.

Gabrovica Viaduct – the launching construction method

The launching method of viaduct construction is an innovative technique whereby prestressed reinforced concrete elements, which are manufactured in segments in the factory, are pushed forward over supporting piers. This advanced technology allows builders to construct the viaduct in increments without the use of traditional formwork supports, which helps projects to be completed more quickly and more safely.

Vinjan Viaduct – free cantilever construction

The free cantilever construction method is suitable for large spans between viaduct piers. Such bridges span high valleys and difficult to reach locations. In this construction method, the deck construction grows to the left and right of the viaduct piers, which is typically done symmetrically on both sides. The shape of the deck construction is generally a box of rectangular or trapezoidal shape in cross-section. This construction technology was developed about 50 years ago.

Bekovec Landfill

Construction site landfills are areas intended for the collection, separation and disposal of construction waste and residual construction materials. These landfills are important for the efficient management of waste on construction sites and have several important functions. They are used to collect and separate different types of waste, allowing for recycling or appropriate disposal. Landfills allow construction materials that can no longer be used to be safely disposed of from the construction site, contributing to a tidier and safer working environment. In addition, construction site landfills also serve as a source of secondary raw materials, as some waste can be recycled and reused in other construction projects. Construction site landfills are important for efficient waste management and sustainable construction.

The Bekovec landfill is located close to the torrential valley of the Krniški potok stream and was used during the construction of the motorway for the disposal of excavated material. The area was not fully filled at that time, and is therefore being used in the Second Track project for the surplus materials generated during the tunneling works. Once the disposal of the excavated material has been completed, the area will be redeveloped by bringing in fertile soil and reclaiming the area. The company 2TDK will plant an olive grove which will then be handed over to the landowners for management.

The seven tunnels on the route

The new railway line starts behind the railway station at Divača, where the existing Divača-Koper line branches off. A good two kilometres later, the line passes into the Lokev tunnel, continues to the Glinščica viaduct, and then on to the Beka tunnel, ending at the Karst Edge. Next comes the Gabrovica viaduct, then the short tunnels Stepani, Tinjan and Osp, and then the line turns south in the Mlinarji tunnel and continues along the Vinjan viaduct. The line then enters the last tunnel, Škofije, and exiting it, continues along the open part of the route through the valley of the Rižana River, finally connecting to the Koper freight terminal.

Lokev Tunnel (T1)

With a length of 6714 metres, it is the longest tunnel of the new line. Like the Beka (T2) and Škofije (T8) tunnels, it is a double-bore tunnel, which means that parallel to the main tunnel tube, a service tube runs in the same cross profile. In the Lokev Tunnel (T1), there are 13 cross-passages connecting the two tunnel tubes at intervals of up to 500 metres, providing safe escape in the event of an accident via escape and intervention routes, while at the same time allowing for efficient maintenance and room for the installation of electrical and mechanical equipment, signalling and telecommunications equipment, and fire hydrants.

Beka Tunnel (T2)

It is the second longest tunnel on the route, 6017 metres long. The main tube and the service tube are connected by 13 cross-passages.

The tunnel runs largely in carbonate rock (about ¾ of its length), and to a lesser extent in transitional layers, which are found at both ends of the tunnel and in intermediate layers of carbonate rock. As in the other tunnels of the Second Track, the NATM technology (the so-called New Austrian Tunnelling Method) is used – the method of tunnelling and mining rather than boring.

Stepani Tunnel (T3)

This is the shortest tunnel on the Second Track, 335 metres long, and the first tunnel from the direction of Divača, just beneath the Karst Edge. Along with the Osp Tunnel (T5-6), it is classified as a short tunnel which, due to its length, does not require forced ventilation and escape routes, which in medium-length and long tunnels are provided by lateral escape tubes or by cross-passages into the parallel service tube. There are no inhabited buildings on the surface in the impact area of the construction of this tunnel.

Tinjan Tunnel (T4)

The Tinjan Tunnel is a single-bore tunnel and, at 1,949 metres, is the fourth longest tunnel on the Second Track route. It also has two exit tunnel tubes. Excavation works in the tunnel started at the beginning of June 2022 and were completed in February 2024. There are no inhabited buildings on the surface in the impact area of the construction of this tunnel.

Osp Tunnel (T5-6)

Originally, two tunnels were planned in the area of the Osp Tunnel, but in later phases the two planned tunnels were merged to form a single Osp Tunnel, 513 metres long.

It is characterised by its pronounced sloping location and two areas of low overburden, where preliminary surface measures were necessary to ensure underground excavation, in the form of the removal of a layer of poor soil and rock and its replacement with cement stabilisation.

Mlinarji Tunnel (T7)

T7, i.e. the Mlinarji Tunnel, takes its name from the nearby hamlet of Mlinarji. With a length of 1154 metres, it is one of the medium-length tunnels on the Second Track. It is built in a single-bore design, with a 165-metre-long lateral service and escape tube in the middle. There are no inhabited buildings on the surface in the impact area of the construction of this tunnel.

Škofije Tunnel (T8)

This is the third longest double-bore tunnel, with a length of 3808 metres. The main tube and the service tube are connected by 7 cross-passages. The excavation technology in the flysch bedrock was implemented mechanically using a tunnel excavator and hydraulic hammers, as well as by boring and mining. In the area of low overburden in the valley of the Škofijski potok stream, preliminary measures were required for the excavation above the main tube, as well as the removal of the bad soil above the tunnel crown and the construction of a reinforced concrete arch cover.

Karst phenomena

Karst phenomena represent a unique geological feature formed by the effect of water on soluble rock. These phenomena are most pronounced in Karst landscapes, where over long periods of time, water, through infiltration and chemical reactions in the rock, shapes and transforms the surface, creating a variety of terrains and landforms.

Formation of Karst Caves

One of the most important Karst phenomena is the formation of Karst caves. Through its action, water slowly dissolves limestone or other soluble rocks, creating underground channels and caves. These caves can range from small caverns to huge underground labyrinths.

Karst Landscapes

Apart from caves, Karst valleys are also a characteristic feature of the Karst landscape. They are formed by the breakdown of the surface due to rock dissolution and erosion, and form characteristic depressions such as Karst poljes or Karst sinkholes. Another important Karst phenomenon is the Karst springs and sinks. Springs are places where groundwater returns to the surface, while sinks are places where water flows back underground.

Karst phenomena also have a major impact on biodiversity, as many species are adapted to the specific conditions of Karst environments. Despite their beauty and importance for the environment, Karst landscapes are vulnerable to human impact and require careful management and conservation.

Karst caves are also natural assets of national importance, which is why karstologists study them during the construction of the Second Track and bridge them in such a way as to minimise damage to them.

Locations of Karst Phenomena

Karst caves are natural assets of national importance. On the route of the Second Track, they are located along the longest tunnels on the route – Lokev (T1) and Beka (T2). All newly discovered caves are studied by karstologists, who propose their bridging in a way that preserves them to the maximum extent possible. By April 2024, the total length of newly documented cave tunnels was 4,815 metres and the total depth was 2,220 metres. The longest and deepest cave discovered is the 2TDK-017 cave, 530 metres long and 168 metres deep. It is about half as long as 2TDK 041, which is 273 metres long and 64 metres deep. By the end of April 2024, 82 Karst caves were documented.

Environmental protection, conservation and monitoring

The construction of infrastructure can have a certain impact on the surrounding area, which also holds true for the construction of the Second Track, despite the fact that the line avoids agglomerations to the greatest extent possible, and 75% of the line runs underground, which, in conjunction with the train as the mode of transport, has particular ecological and sustainable advantages. The siting of the Second Track was based on the most environmentally friendly solutions, since the line passes through environmentally sensitive and protected areas. Despite major construction activities, the environment has been kept as untouched as possible.

The greatest impact on the environment comes from construction.

This is why extensive environmental monitoring is conducted, mitigation measures are implemented and immediate action is taken should the situation worsen. This is how we look after the environment and protect and preserve nature.

To preserve and protect the environment, we monitor fish and crustaceans, amphibians, birds, habitat types, aquatic organisms and bats. Because of the Karst terrain, karstological monitoring is also conducted. As part of the monitoring, the population baseline was recorded and the monitoring shows the impact of the construction. Because the forest was felled to build access roads to the construction sites and many bat roosts were lost in the process, replacement roosts, known as bat boxes, were built. There are 45 permanently installed in specific locations, and are slowly being colonised by bats. With a third of the bat boxes now occupied, this shows that the bats have discovered and accepted them. And they have not only been colonised by the species recorded before construction, but also by a new bat species originating from Italy. Monitoring of water and aquatic organisms is extremely important in the area of the Second Track. Regular inspections are conducted in the areas of the Glinščica valley, the Osapska River and the Škofijski potok stream.

Alongside environmental monitoring, noise, air and vibration monitoring is also conducted during construction, and major infrastructure is regularly inspected.

We are aware of the importance of a healthy environment for humans, flora and fauna. Despite the complexity and magnitude of the railway construction project, we are demonstrating that the measures we are taking and the monitoring we are conducting have largely preserved the environment and its organisms, and that in some places some improvement has even been detected. Measures for nature conservation during the construction phase are complex and numerous. There will be no permanent negative impacts on nature during the operation of the line, as nearly the entire line runs underground. Moreover, owing to the route of the line and the way it is constructed, fire safety will also increase considerably.

Some plant and animal species along the route

White-clawed crayfish

It lives in Europe’s fresh waters, where it hides under rocks and in places where it is safe from predators and strong water currents. On the route of the Second Track, it is mainly found in the Glinščica stream. The white-clawed crayfish only inhabits unpolluted watercourses, which means that despite extensive construction works, the watercourses in the Glinščica valley remained clean, and the continued presence of the crayfish is a further indicator of the good environmental status of the water.

Amphibians

Amphibian monitoring follows the life cycle of amphibians at individual monitored sites, such as puddles, ponds and wetlands. Nine species of amphibians have been recorded in the studied area, namely the common toad, the agile frog, the northern and southern smooth newt, Italian crested newt, the fire salamander, the European tree frog, the yellow-bellied toad and the common water frog.

Tree of heaven

It is a non-native invasive plant species native to China. Being a fast-growing tree species, it was used in the 19th century to reforest bare Karst areas. It is precisely because of its rapid spread that the tree prevents the growth of native plants, and therefore its spread must be carefully monitored and appropriate action taken. The tree of heaven is the most common of the non-native species found on the construction sites of the Second Track.

Bats

So far, 33 species of bats have been recorded in Slovenia, one of which is believed to be extinct, bringing the current number of species present in Slovenia to 32. In the Glinščica valley, 13 bat species were identified at the time of the species census the lesser horseshoe bat, the greater horseshoe bat, the whiskered bat, the Savi’s pipistrelle, the common noctule, the common pipistrelle, etc. The loss of bat roost trees due to deforestation has been compensated by the installation of 45 bat boxes.

Birds

Bird monitoring includes a census of nesting birds and the Eurasian eagle-owl along the entire route, and particularly in the Glinščica valley and in the Črni Kal area. This area is home to a large number of different bird species typical of the Karst, including both diurnal and nocturnal species. Species recorded in censuses so far include the corn bunting, the Eurasian hoopoe, the Eurasian skylark and the woodlark, the red-backed shrike, the Eurasian eagle-owl, the scops owl, the nightjar, the tawny pipit and the short-toed snake eagle.

Tracks on the railway line from Divača to Koper

85% of the length of the railway line of the Divača-Koper Second Track will be a slab track, while the open section of the route from the Divača station to the entrance portal of the Lokev tunnel (T1) and from the exit portal of the Škofije tunnel (T8) to the Koper freight terminal is planned to be a ballasted track.

Ballasted track

The traditional ballasted track has a high degree of elasticity and noise absorption. An important advantage of a traditional track is that it is easy to maintain, although maintenance still needs to be done, and more often than with a slab track. Engineers have 160 years of experience in building traditional tracks. The construction system is faster and cheaper. And the life expectancy of a ballasted track is between 30 and 40 years.

Slab track

Slab track is a modern track design, successfully used all over the world, which compared to the traditional ballasted track requires less maintenance, has a longer life expectancy and provides a more comfortable ride. Using the slab track system eliminates the possibility of track geometry errors during maintenance work. Because of the possibility of it being directly attached to structures, its lower structural height and weight compared to the traditional track, this track system is most optimally suited for tunnels and bridging structures. The life expectancy of a slab track is between 50 and 60 years.

Contact

Coordinator of the Kraški rob visitor point:

katjusa.stankovicmaric@visitkoper.si

031 602 020