Notranjska hides in its bosom an underground kingdom, an immense labyrinth of pits, caves, tunnels, and streams hidden from everyday visitors and observers. Underground flow through unknown and only partly discovered tunnels veritable rivers, forming magnificent waterfalls, countless rapids, and true lakes.
It is a magnificent world, especially in places where water has hollowed out big halls into limestone layers. In complete darkness, millions of stalactites of breathtaking shapes and colors have been formed. Beauties of the Notranjska underground have since long been a magnet for visitors.
There is no other place anywhere in the world that could match Notranjska. Subterranean streams regularly resurfacing and singing their brief greeting to the sun soon again disappear into the darkness of the underground world. Spring and autumn rains fill up the famous intermittent lakes. In all this unspoiled nature a visitor finds himself surprised by the rich history of the province.
The Logatec basin resembles a karst polje. The northern part of the valley is called ‘Pusto polje’ and has no water but plenty of potholes and coniferous forests. Through the southern part of the valley runs the Logašcica stream which disappears underground practically in the center of Logatec. In Roman times it was a military camp.
The town later developed from seven villages and lived off the transport trade for centuries.
Near Logatec the old road linking Ljubljana and Koper is joined by the main road from Idrija and Ajdovščina. The road along Pusto polje leads to Žiri and the Poljanska dolina.
The old road leads through Grčarevec along the edge of the Planinsko polje, the most typical karst polje in Slovenia. Planinsko polje stretches Zagora and the Ravnik karst plateau. Planinsko polje is covered with meadows and scarce trees, it is only along the banks of the Unica river that vegetation is denser. The Unica river bed is shallow and very meandering polje which makes it several times longer than the polje. Since the Unica floods the polje nearly every year, the villages are situated on the slopes surrounding the polje.
The Unica springs out from the Planina cave ( Planinska Jama ) at the southernmost point of the polje. A path leading to the confluence of the Pivka and Rak is made through the cave. From the confluence on the river is called Unica. On a hill near the cave entrance is the Little Castle (Mali grad) which belonged to the Raubar aristocratic family. Further down the Unica are the ruins of the early Baroque Habsburg castle which was burnt down in WW II. On the wooded hill above it are the ruins of another old castle. All those castles were used to guard the important passage into the Postojna Gate.
Thick forests under Javomik hide a pearl – the Rakov Škocjan valley, also called the Rak valley. Ceilings of underground caves have collapsed and today the Rak runs in broad daylight. At both ends of the valley, parts of the ceilings were preserved, thus making two wonderful bridges – Mali naravni most at the eastern end and Veliki Naravni at the western end of the valley. The Rak flows in from Cerknisko polje through a cave under Nesrecni grič hill ( 712m ).
The vast meadows of Lake Cerknica are filled with water in rainy periods. Its surface is then up to 24 km2. When the water starts disappearing, numerous streams wind like snakes across the field, and you can also the swallow holes through which the water flows underground. One of the larger swallow holes is Peseta near Dolenja vas pri Cerknici. The water also disappears underground through numerous subterranean caves. It resurfaces again in the Rakov Škocjan, but the Rak River is only 2 km long before it disappears underground again. In the dark shafts of the Planina cave, the Rak joins the Pivka River which comes from the Postojna cave. After the confluence, the river is called Unica and it resurfaces again in the Planinsko polje.
At the other end of the polje, it disappears again and resurfaces near Vrhnika as the Ljubljanica.