4250 caves are known in Bulgaria until now. A great part of the territory of the country is covered by carbonate rocks. Among them are 3 sandstone caves and 60 caves in volcanic rocks. Bulgaria has 6 show caves.
The longest caves are Duhlata (L=17,500m), Orlova Čuka (L=13,437m), and Iagodinska Peštera (L=8,250m). The deepest caves are Raychovata Dupka Cave (-372m), Barki N14 (-350m), and Kipilovo (-350m). The deepest shaft is found at Druzhba (-130m). However, the Bulgarian cavers were very successful during the last years in discovering and exploring new caves, so this may change.