The Carso (Karst): Caving Paradise in the Far North-East of Italy.

You need little etymological skill to deduce Karst from Carso. Believed to derive from kar, a word of Celtic origin meaning ‘a rocky place’ – also the root of Carnia and Carinthia, two nearby mountainous regions – it now denotes a brand of limestone scenery of which this region is the archetype.

The Karst Plateau (Slovenian Kras) – also simply known as Karst – is a limestone borderline plateau region extending in south-western Slovenia and north-eastern Italy. It lies between the Vipava river, the low hills surrounding the valley, the westernmost part of the Brkini hills, northern Istria, and the Gulf of Trieste. The western edge of the plateau also marks the traditional ethnic border between the Italians and Slovenians. The region gave its name to the Karst topography; for this reason, it is also referred to sometimes as the ‘Classical Karst’.

A slender ledge that reaches down the north-eastern coast of the Adriatic from Monfalcone to Trieste, the Italian Carso is the only section of the Istrian peninsula still belonging to the country, the rest having been ceded to former Yugoslavia after WW2 – and therefore part of what today are Slovenia and Croatia. Nonetheless, despite the political/administrative conundrum, much of this hilly region forms a geological – not to say cultural – unity, with Slovenian as the main language. According to geographic conventions, however, Istria belongs to the Italian geographic region. (the area was also under Venetian rule for centuries) This is the region’s chief appeal, bringing a little piece of the Balkans within the Italian traveller’s grasp.

Geographical Position

The Carso plateau rises quite steeply above the neighboring landscape, except for its north-eastern side, where the steepness is less pronounced. The plateau gradually descends from the southeast to the southwest; on average it lies 334 m above sea level. The highest elevation is Mount Snežnik (Monte Nevoso in Italian; 1.796 m). Its western edge, known as Karst rim, is a continuation of the Ucka mountain range in eastern Istria, and it rises to the east and southeast of Trieste, ending in steep cliffs between Aurisina and Duino. Many interesting geological phenomena occur along the Karst rim, including the picturesque Val Rosandra (Rosandra valley; Glinščica in Slovenian).

Because the Carso steeply descends towards the Adriatic sea, it is less exposed to the beneficial climatological effects of the Mediterranean. In the past, the vegetation on the plateau was mainly composed of oaks, but these were replaced by pine forests in the 19th and 20th centuries. Starting as far back as the Middle Ages, the plateau suffered radical deforestation for economic reasons; forests now cover only one-third of the Karst. Although much of the wood for the closely spaced poles that support the island city of Venice also come from this region, the Republic carefully managed the Karst forests as a reserve for naval timber. The most radical deforestation actually occurred in the mid-nineteenth century, due to clear-cutting by local farmers and conversion of the land into pastures for sheep.

The Carso is particularly famous for its caves. In Slovenia, there are several  well-known caves, including Skocjanske Jame (Grotte di San Canziano), briefly described below (but see also the dedicated page), and the Grotte di Postumia in Slovenia; in Italy, the Grotta Gigante is the largest show cave in the world (also, read below).

Most of the Karst is located in the Slovenian and Julian littoral, covering an area of 429 square kilometres, with a population of about 19,000 people (this excludes of course the city of Trieste, which in itself has a population of nearly 400,000). The Carso as a whole has around 100 main settlements, puls innumerable small hamlets and isolated farmsteads. The town of Sezana is the center of the region on the Slovene side of the border; in this context, however, we will only deal with the Italian side, where the main municipalities – apart from Trieste – are Sgonico/Zgonik; Duino-Aurisina/Devin-Nabrezina; Monrupino/Repentabor and San Dorligo della Valle/Dolina.

Natural conditions – including the bora wind (Slovenian burja), and the local way of life – all shaped the elements of Karst architecture, creating simple but well-defined forms (see Marbles and Ornamental Stones, below). The Karst is also renowned for its strong red wine, known as Teran, and its ham (read the tradition of the osmize, also below).

The Diversity of Flora

The Carso is one of Europe’s great environmental crossroads: a mix of Central European, Alpine, Mediterranean and Balkan habitats, with a correspondingly diverse range of flora and fauna.

The region contains one of the highest tallies of endemic plants in Italy, with no less than 1,900 distinct species. One of the most remarkable native plants is a Knapweed, Centaurea kartschiana, whose solitary heads of tiny pink flowers refuse to grow anywhere but under a drenching sea spray along the Carso coast. Plants like this must be hardy enough to weather both the intense summer heat and the icy winter blast of the bora – a buffeting north-easterly wind so strong that railings are fixed along the steepest streets of Trieste for people to grab.

Every season carries its bounty: spring, delicate with the blossoms of Hawthorn, Plum and St. Lucy’s Cherry (Prunus mahaleb); summer, ablaze with wild Roses, Peonies (Paeonia officinalis), Gentians (amongst which is the endemic Trieste Gentian, Gentiana tergestina) and more than 30 species of Orchid; autumn, bringing scented purple Cyclamens (Cyclamen purpurascens), the statuary Giant Bellflower (Campanula pyramidalis) – and much besides – to add to the woodland’s riot of colour. But the Carso is perhaps at its most photogenic at the fading of autumn into winter, when entire hillsides covered in Red Sumac (Cotinus coggygria) blaze with the intensity of a deep sunset; the bushes tinted – so the locals say – with the blood of over 100,000 soldiers who lost their lives here during WW1.

Flowers alone, in most people’s minds – let alone the rocks – would be enough to justify a visit here. The Carsiana Botanical Garden has attempted the Herculean task of collecting at least a fraction of the region’s remarkable flora. The garden is divided into 8 areas, each replicating a different local habitat of the Carso, and it is situated between Gabrovizza and Sgonico/Zgonik. Refer to the dedicated page to have more detailed information on the garden.

Karstic Geologic Phenomena and Other Sights

The plethora of limestone features provides another compelling reason for a visit. The sights start along the coast, which is fringed by the low Duino cliffs (now a Nature Reserve), themselves an unusual sight along the Italian Adriatic coast, which – give or take the occasional Conero or Gargano promontory – is all but flat. Many of the cliffs are sculpted into strange shapes, almost waves of stone: the best are around Duino, Sistiana and Miramare (which has also Italy’s only underwater WWF reserve).

Inland, erosion of the permeable limestone has produced more than 2,000 caves with a honeycomb of galleries and subterranean lakes, swallow-holes and dry valleys. The baffling Timavo river (Reka in Slovene) rises across the border in Slovenia and then flows underground for 40 kilometres, to finally emerge in Italy very close to its outlet into the Adriatic sea, with a volume 25 times as great as when it disappeared. Even more extraordinary is the Grotta Gigante – the largest cave in the world open to the public: 107 metres deep and 208 metres wide, it would be large enough to swallow St. Peter’s church in Rome within it! The impressive Skocjanske Jame (Grotte di San Canziano), briefly described below (but see also the dedicated page), and the Grotte di Postumia are in nearby Slovenia.

Both the Grotta Gigante and Miramare are next to Trieste and can be easily reached via  a short stretch of superstrada (dual carriageway), and/or minor roads. The land part of the Miramare reserve is open daily, while to visit the underwater section one must book with WWF; scuba diving is also available during weekends.

Bird-watchers cluster around three small areas of wetland on the Doberdò lake, best known for its eight-metre changes in water level; a fluctuation that yields a rich variety of aquatic flora and fauna. Many hundreds of terns are its main attraction, but other bird species occupy this and other habitats of Carso too, in high numbers, all year round.

The Grotta Gigante

The Grotta Gigante (Giant Cave, Briška jama in Slovenian) – open since 1908 and also known as Riesengrotte in German or as Grotta di Brisciachi – is a giant cave on the Italian side of Carso, in the municipality of Sgonico/Zgonick. Its central cavern is 98,50 m high, 76,30 m wide and 167,60 m long, putting it in the 1995 Guinness Book of Records as the world's biggest tourist cave, with the largest inner chamber (a total volume of 350,000 cubic meters).

This is a fascinating place, located not far from Trieste city centre and easily reacheable from it (indications below), where tourism, environment and scientific research blend together. The cave contains many large stalactites and stalagmites, many of exceptional beauty. A feature of the stalagmites is their "dish-pile" appearance, formed by water dripping from up to 80 m (260 ft) above and depositing calcium carbonate over a wide area.

As said previously, the enormous hall is 98,50 m high, 76,30 m wide and 167,60 m long. A steep path with atmospheric electric lighting allows the visitor to spend about 1h15 minutes (access with a guided tour only) in this amazing underground space, with its rich calcite concretions – the highest of which is no less than 12 m high.

The available space and the constant temperatures throughout the year have led to the placement of two geodetic pendula in the cave (which hang down from about 100 m, and are the longest in the world), and of other scientific instruments.

The cave was first explored by A. F. Lindner in 1840. At the time, the Karstic region behind Trieste was being searched for underground water from the Timavo/Reka river, in order to supply the city through a newly built aqueduct. In 1897 the Grotta Gigante was fully mapped, then properly equipped for guided tours in 1905, and finally inaugurated in 1908. After World War I, ownership went to the Julian Alpine Society, but tourism only really began in earnest in 1957, after the area definitely became Italian – and that is also when electricity was installed, unveiling new perspectives and details.

A Museum of Speleology is near the cave, and besides the various speleological, geological and paleontological objects, it also includes some valuable archeological finds, and a poster collection of the cave. Two wide parking lots are available on the outside; visits are scheduled at several times of the day (usually on the hour, but check before a visit) and must take place with the aid of expert guides. The tour of the Grotta Gigante lasts about 1 h 15, and a specialized guide will take the visitors through a 850-metres long path, descending to about 100 metres underground. The temperature inside the cave is an average 11 degrees C all year round – so warm clothing is recommended.  

Access. The Grotta Gigante is located about 10 km away from the centre of Trieste. If you are coming by car, take via Coroneo and go straight on uphill until you reach the small town of Opicina, then follow the signs to Borgo Grotta Gigante and the cave. If you are coming from the A4 highway, exit at Sgonico (from Venice) or Prosecco (from Trieste), and in either case follow the signs to Borgo Grotta Gigante. By bus from the city centre: No. 42 from Piazza Oberdan, or near the station. 

Skocjan Caves in the Slovenian Kars

The Miramare Underwater Reserve

Miramare has been one of the first such reserves to be officially established in Italy, and it is entrusted to the Italian Association WWF for Nature. It is also a UNESCO Biosphere Reserve site.

The Miramare Underwater Reserve is located in the Gulf of Trieste (Northern Adriatic), around a natural promontory that commands astonishing views over the Grignano bay (Baia di Grignano), on which the famous Castle of Miramare (Castello di Miramare) is also placed. It includes a coastline of 1,700 meters and an offshore area of 120 hectares, divided into a core zone (30 hectares) and a buffer zone (90 hectares).

In respect to other Mediterranean Reserves, much more isolated, the level of human impact at Miramare is extremely high since the promontory is placed between the touristic port of Grignano and the Barcola seashore, used as a beach by the inhabitants of Trieste. The reasons for the protection of the promontory are found in the peculiar geomorphological characteristics of the local flora and fauna, because of which Miramare is a unique environment in its own right, and that alone can represent the peculiarities of the Gulf of Trieste. Some of the major ecological characteristics include:

– tidal flats with significant tidal range (about 2 m);
– high temperature variation in the water column;
– fresh water flows from rain and several water systems (Isonzo, Timavo and Tagliamento rivers all drain in the vicinity);
– coastal currents influenced by strong winds;
– both soft and hard bottoms represented along the coast;
– input of new oxygenated water into the Mediterranean Sea (in winter);
– eurihaline and eurithermal benthic communities, some of them well adapted to intertidal conditions.

The Reserve reaches a maximum depth of 18 meters and presents a series of various types of seabeds found near the coast and further away from it. They go from the rocky habitat made up by calcareous rocks, descending from the Karst highlands directly to the sea, to sandy and muddy habitats. The different environments are characterised by high levels of biodiversity and populated by a variety of animal and plant species of high conservation value, which represent most of the natural features and characteristics of the Gulf of Trieste.

Despite being one of the smallest reserves on the Mediterranean Sea of such type, Miramare has always been a model for effective and up-to-date management, where socio-economic and conservation issues are tackled with an integrated and comprehensive approach. The Reserve collaborates with national and international institutions and it is part of the WWF-Italy Oases and Protected Areas network. It can therefore be considered a first-rate cultural, educational and scientific entity, dealing with three major issues: conservation of marine and coastal zones; environmental education and popularisation; monitoring and investigation of the marine ecosystem.

Doberdò del Lago (Doberdò Lake)

Doberdò (Slovene: Doberdob) is the only municipality in the Province of Gorizia that lies entirely on the Carso plateau. The Doberdò area has a crucial strategic position. Throughout the middle of the municipality, in fact, runs a relatively wide and flat canyon that stretches from north to south, connecting the Vipava valley to the Adriatic sea. The canyon is called simply Dol (Slovene for 'vale'). The main road between Gorizia and Trieste runs through this canyon, which is the most direct connection between the Goriška region and the seaside.

At its southern edge, the Dol canyon widens into a typical Karst polje (Karstic field), dominated by Lake Doberdò. The village of Doberdò is located west of the Dol canyon, on an elevated section of the plateau known as Doberdò Karst (Carso di Doberdò; Doberdobski Kras). On the eastern side of the Dol canyon rises the plateau known as Trieste and Komen Karst, which continues eastward and southward into neighboring Slovenia. The Dol canyon ends in the narrow Timavo/Reka valley, which is already located in the neighboring municipality of Duino.

Lake Doberdò (Italian: Lago di Doberdò, Slovene: Doberdobsko jezero) is in fact the name of a sinkhole. It is named after the homonhymous village, and it is located on the westernmost edge of the Karst plateau, close to the border with Slovenia.

It covers an area of approximately 0.36 km², depending on the time of year, and it is located around 2 km southwest of the village of Doberdò, not far from the Adriatic coast. The water is filtered through various ponors (natural surface openings), and it is connected with the springs feeding the Timavo/Reka river, which are situated a few kilometers to the south-east; the depth varies from 5 to 10 m. The lake is usually at its largest in autumn, when it is 1.2 km long and about 350 m wide. During the frequent periods of drought, the expanse of water almost completely dries out, and the site becomes a marsh-like area.

The Timavo/Reka River

The Timavo river, known in Slovene as the Timava or Timav as it gets close to the estuary and Reka in the upper valley (before disappearing underground), is a 2-km river in the Province of Trieste. It has four sources in San Giovanni (Slovene: Štivan), near Duino, and outflows in the Gulf of Panzano (part of the Gulf of Trieste), three kilometers southeast of Monfalcone.

The river has a typically Karst character. It receives much of its water through subterranean flow from the Reka river (Slovenia), but tracer studies have shown that other sinking rivers – Vipava, Soča, and Raša – also contribute. From modelling results, the Timavo/Reka system is believed to receive one third of its flow from the Reka, two-thirds from infiltration of precipitation into the Carso plateau, and to a lesser extent from other sinking river sources.

The Roman authors Livy, Strabo, and Virgil already mention the river; Virgil wrote that nine streams emerge from a mountain to form the river. A Roman settlement near the springs was called Fons Timavi (literally, Timavo Springs), while the whole area was considered an important sacred site, equal for relevance only to the Clitumno Springs in Umbria.

A Varied Fauna

The Carso’s fauna is hard to spot but well-worth looking out for. Herds of Roe-deer are common in the remnaining tracts of Black Pine and Oak forest, and there have been occasional sightings of Bear and Lynx. Lower down the food chain, the range of climates and habitats yields scores of endemic invertebrates, as well as several typically Balkan reptiles, which are unknown further west in Europe. These include the Balkan Whip Snake (Hierophis gemonensis), the Dalmatian Wall Lizard (Podarcis melisellensis) and the Dalmatian Algyroides (or Blue-throated Keeled Lizard, Algyroides nigropunctatus, whose male is distinguished by its orange-red belly and blue throat); Horvath’s Rock Lizard (Iberolacerta horvathi) is only known in the Karst regions of north-eastern Italy and Slovenia.

The most extraordinary creature of the area, however, is by far the Olm  (Proteus anguinus) – a cave-dwelling amphibian similar to the salamander, (it is in fact an aquatic salamander) and the only member of its family in Europe; its nearest relatives live in eastern North America. This animal is most notable for its adaptations to a life of complete darkness in its underground habitat. When fully grown, the olm retains larval characteristics, including prominent gills, but it is able to reproduce – a feature known as 'neoteny'. This creature is so famous in the area to have been adopted as the symbol of Slovenian natural heritage

Mountain Huts in the Carso Area

The mix of nature and history makes the Carso plateau an unmistakable area: travel by bike or by foot with stops to eat and drink in the local agriturismi and “osmize”; follow the branches hung on the side of the roads and you will get to treat your palate to the typical olive oil and wines (more on this below). However, if you are aiming for something more 'Alpine' in style, you can head for the picturesque Val Rosandra (Rosandra valley; Glinščica in Slovenian) instead, in the municipality of San Dorligo della Valle/Dolina. 

From the National road or from Trieste get to Bagnoli della Rosandra and follow the stream towards Bagnoli Superiore. Cross the town, and the road will take you to an Alpine lodge  – the only building with such characteristics in the area. The Rifugio Mario Premuda (mountain hut) is located on the left bank of the Rosandra stream, in the Rosandra valley – the largest division in the Carso plateau. The environment here is particular: the stream, the vegetation, the rock faces and the caves all remind one of Alpine landscapes, even though we are quite close to the sea. The hut  is open all year-round except on Tuesdays and in February, and is a convenient facility for walks in the area; the Val Rosandra Rock Gym is also nearby.

Language, Culture and Traditions

The vast majority of the inhabitants of Carso are ethnic Slovenes. They speak two closely related Slovene dialects, both belonging to the Littoral dialect group. In the southern part of the plateau (in some Slovenian municipalities – including part of Sežana –, in the Italian municipality of Monrupino/Repentabor, and in most of the Slovene-speaking areas of the municipality of Trieste), an Inner Carniolan dialect is spoken. In the northern section (the remaining part of the Sežana municipality, in other Slovenian municipalities, in the Italian municipalities of Sgonico/Zgonik, Duino-Aurisina/Devin-Nabrezina and Doberdò del Lago – as well in some suburbs of Trieste, like Barcola), the Karst dialect is spoken instead.

The Carso is famous for its red wines and its traditional cuisine, which is a mixture of Mediterranean, Central and Eastern European influences. The traditionally produced Karst prosciutto – a sort of dry-cured ham – is protected at European level. All of these can be tasted in the traditional inns known as “osmize”. 

The Tradition of the “osmize”

The tradition of the “osmize” (osmice in Slovenian) in the Carso dates back to the Austrian-Hungarian period, when farmers were granted the right to sell non-bottled wine or other agricultural products for a period of eight days in a year; hence the term ‘osmica’ (in Slovenian osem means eight) – or ‘osmiza’ in the dialect of Trieste. Today, the local farms that apply for the permission to open are granted this possibility by the municipality where they are situated, which guarantees for the quality and genuineness of the products sold. A suspended branch, normally of ivy (also known as ‘frasca’ in Friuli), with an arrow, and set along the road – usually at a crossroads – indicates the direction towards a nearby open ‘osmiza’.

Other typical products of agricultural farms are sold twelve months a year. For more precise information about the opening time of the single 'osmize' one should contact the individual municipalities (which in the Italian Carso inland of Trieste are four; a booklet that lists all the 'osmize' is also available from the Trieste tourist office).

Other Notable Features: Marbles and Ornamental Stones

The marbles and ornamental stones represent a precious natural resource of the Karst plateau surrounding the city of Trieste. The origin of quarrying and stonework dates back to Roman time, and the large use of limestone in building is still visible in many villages of Carso. Characteristic elements are the entrance portals, the windows, the (now rare) stone-flagged roofs and other ornamental elements (i.e. wells) – all made out of limestone, and decorated with different traditional symbols.

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