http://en.wikipedia.org/wiki/Matmata,_Tunisia

Matmata (Arabic: مطماطة‎ Maṭmāṭah) is a small Berber speaking town in southern Tunisia. Some of the local Berber residents live in traditional underground "troglodyte" structures. In 2004 it had a population of 2,116.[1] The structures typical for the village are created by digging a large pit in the ground. Around the perimeter of this pit artificial caves are then dug to be used as rooms, with some homes comprising multiple pits, connected by trench-like passageways