For any fan of rock formations, this has to be on the list of things to see. An underground city of more than 10 levels honeycombing beneath the surface. Probably built in the 7-8th century, but possibly as early as the 5th century (AD), it housed between 3000 to 50,000 people. Instead of hauling up a draw-bridge, when security was required, stone doors were rolled into the entry ports. Religious persecution is said to be the inspiration of this complex and fascinating refuge.
