Tora Bora (Pashto: توره بوړه, "Black Cave") is a cave complex, part of the Spin Ghar (White Mountains) mountain range of eastern Afghanistan. It is situated in the Pachir Aw Agam District of Nangarhar, approximately 50 kilometres (30 miles) west of the Khyber Pass and 10 km (6 mi) north of the border of the Khyber Pakhtunkhwa province in Pakistan. Tora Bora and the surrounding Spin Ghar range had natural caverns formed by streams eating into the limestone, that had later been expanded into a CIA-financed complex built for the Afghan mujahideen. Tora Bora was known to be a stronghold location of the Afghan mujahideen, used by military forces against the Soviet Union during the 1980s.