Istria, due to its soil types (karst and limestone) has a lot of underground caves. Several of them can be visited without a lot of speleological knowledge and equipment while for a large number of them, however, You need more experience and specialized equipment.
Underground chambers, lakes, streams, pits, gorges, crevices and petrifactions will surely inspire each visitor with enthusiasm. Apart from natural beauties, Istrian caves and pits are a treasury of animal and plant world (fish, frogs, dormice, crabs, bats), the most interesting among them being Proteus anguinus, endemic species that inhabits only these Karst areas.
The world-famous abyss Pazinska jama has gained popularity thanks to Jules Verne who described it in his novel 'Mathias Sandorf'. Some 1500 caves have been registered until today, and each year there are about 10 more newly discovered ones.
Visit the underworld the Baredine Cave. This cave is a treasure chest of stalagmites and stalactites, underworld sculptures created through time by the patient work of water
Ćićarija in the north of Istria is a separate Karst entity with the deepest Istrian pit called Rašpor, 361 m deep.
Near the town of Roč are abysses Krkuž and Gragorinčići. The longest cave in flysch is Piskovica in central Istria, 1.036 m long. Nearby is also Marfanska pit, 273 m deep and with its 2,045 m of explored underground passages is the longest cave in Istria.
Batluška pit has the largest chamber, 200 m long and 150 m wide, measuring a height of 60 m.
The north-western areas, where flysch layers come in contact with limestone, are specific for the great number of abysses. An exceptionally picturesque one is that near Šterna, 231 m deep, and it is specially beautiful in the rainy period when a wonderful waterfall forms, creating a lovely small lake at the bottom of the valley before disappearing underground. In the vicinity is an old abandoned mill. Specially interesting is the Karst zone of western Istria covered with red soil, so that very often stalactites, stalagmites and crystals are vividly red.
In addition to pits, caves are very interesting speleological sites as well. Because of its accessibility, the presence of people and animals in them goes back into the distant past so many of them are today still interesting archaeological and paleontological sites: Šandalja, Vergotinova, Romualdo's Cave, Trogrla, Mramornica cave, Feštinsko Kraljevstvo cave… are only some of them.