Búðahraun was declared a nature reserve in 1977. The volcano in the middle of the lava field is called Búðaklettur. Despite the name (klettur meaning 'rock'), it is not a rock, but an 88-metre deep crater from which the lava flowed some 5,000-8,000 years ago. The eastern part of Búðahraun is ropy lava and features a number of caves. The best-known is the Búðahellir cave.