Bileca Lake is a large man made lake on the Trebijanca River in the municipality of Bileća. The lake was created in 1968. This is the only source of surface water in an area which is subject to extreme weather conditions in winter and also in summer. Cepelica is its small tributary in Bileća Rudine and is stated to be the best known subterranean river in Bosnia and Herzegovina. It lies in the Upper and central part of Trebsinjica valley 17 km from Trebinje is one of the largest lakes in the country.
The landscape of the district where the lake is situated consists of lime stone mountains with bare karst formations.