The Ljubljanica is about 40 km long river in Slovenia, a right tributary of the Sava river. Ljubljana, the capital of Slovenia, is located on the river, and confluence with the Sava river lies about 10 km downstream from Ljubljana. It has two karstic sources - the Trbuhovica and the Pivka river. More than 20 km of the river flows underground in caves, and because of this the river is known under seven different names (Trbuhovica, Obrh, Stržen, Rak, Pivka, Unica and Ljubljanica). This makes it one of the most interesting rivers in Slovenia, in spite of its short length.