Cave Bolii is 6 kilometres far to the north of Petrosani. To get there you must pursue the road that ties Valea Jiului to Tara Hategului ending up where Muntii Retezatului meet the ones of Sebes.
The name of the cave comes probably from the Bolia family which owned land and forests in the area in the XV century.
The cave’s entrance is 20 metres long and 10 metres high.
The Bolii’s is of big dimensions containing even large rooms. Despite the fact that it is 466 metres long, the cave doesn’t really „sink” in the ground as the leveling does not.
The cave Bolii is one of the few caves of its kind in this country. Most of the caves have only one entrance but this one has 2, going from one side of the mountain to the other side.
The cave was abandoned until the local speleologists have decided to improve its conditions so that it can be visited by tourists.
Since the interwar period, musical concerts have been organized in a specific hall. The hall was named „Sala de concert si dans” (The Hall of concert and dance) due to its incredible acoustics.
There are 2 species of bats that live inside the cave.
Cave Bolii belongs to the protected area of the Natural Park Grădiştea Muncelului- Cioclovina having 8 reserves, natural monuments and historical monuments such as: The Dacian Fortress „Bolii” or „Castrul de la Crivadia”.
Due to the large underground space of the cave, the germans have chosen the filming of some of the scenes from the documentary „Legenda Nibelungilor”.