TThe ridge of the Balkan Range is the main watershed between the Black Sea and the Aegean. To the North, towards the river Danube and the Black Sea flow the rivers Vit, Osam and Rossitsa, while to the South, towards the Aegean, rush the Topolnitsa, the Stryama and the Tundja. The deep karst bedrock provides a steady outflow of the underground aquifer feeding those rivers, and the sprawling old forests retain the topsoil moisture. The riverbeds are steep, the rivers are fast and abundant in water.

   At many places these rivers jump off high cliffs, forming scenic waterfalls, which the local population calls praskala, or spray gushers. Central Balkan is the scene of some of the highest and most impressive waterfalls in Bulgaria, notably Raiskoto Praskalo (124.5 m.), Vidimskoto Praskalo (80 m.) and Kademliiskoto Praskalo (72 m.).

   IThe gross average annual outflow of all water streams generated in the territory of Central Balkan National Park is 460 million cubic meters; however, this may drop to 290 million cubic meters on a dry year, or rise to 530 million cubic meters on a rainy year. The local water is of very high quality and makes up a large portion of the drinking water resources of Bulgaria.

   The present-day mountain relief in Central Balkan National Park is the product of mighty geological processes, refined over millennia by water and wind. Rounded ridges and high peaks alternate with deep canyons, vertical rock faces and caves. The Balkan Range is the central structural mountain strip in the Balkan Peninsula. It is made up of several basic types of rock, most commonly southern Bulgarian granites, sandstone, crystalline schists, etc. At altitudes over 1,800 meters above sea level there is some evidence of glacier activity in the geological past.

   Mountain cliffs and rocky landscapes occupy about 2,000 hectares (3% of the entire Park territory). Among the more original natural formations are Skalniya Most (the Rock Bridge), Markovata Dupka (Mark’s Hile) and the spindly vertical Kalchovi Kamani stone pillars. In the Park is located the unique Djendemite (literally: the Hells) rock complex combining centuries-old forests, vertical rock faces, and a mighty strip of exposed rock, that is one of a kind in Bulgaria. Another unique formation is the system of gorges and canyons that comprises the narrow valley of the river Stara Reka, the canyon of the Cherni Osam river, the valleys of the rivers Sokolna and Byala.

   Though karst bedrock accounts for a relatively small part of the protected area, it is the scene of many deep caves and precipices. Remarkable for its bottomless caves is Steneto Reserve, where Raichova Dupka, the deepest precipice cave in Bulgarian (377 m. in depth, 3,333 m. combined length of all galleries) is located; also here is Kumanitsa, the longest flooded cave in Central Balkan (1,656 m. explored length, average outflow of the underground river 600 liters per second).

   The caves and canyons, the rock faces and cliffs are inhabited by sic species of bats endangered on a world scale, by a number of petrophilic birds, and by various rare and beautiful plants.