The Burren, Boirinn, Stony Place, is a unique area in the north west part of County Clare. It is a huge area of limestone pavement. It covers 50 sq miles (130km˛). Surface streams and rivers disappear down pots as they cross from shale to limestone. Because of this the area underneath the limestone pavement is riddled with caves. The easiest cave to visit is Ailwee Cave, which is open to the public. It was only discovered in 1940, and has been opened up with walkways and bridges so that it can easily be seen. The architecture of the entrance building has won awards. The area has many stone forts and dolmens. The whole area was well settled before the Celts arrived in Ireland. There are 70 ancient tombs in the area the most famous being the Poulnabrone Dolmen. In the 1640's Cromwell’s surveyor described it as a savage land, yielding neither water enough to drown a man, nor a tree to hang him, nor soil enough to bury him. Few trees manage to survive here but other plants thrive. In fact the Burren is a very exciting place for those interested in plants. From May to August the warmth the limestone gives and the shelter plants receive in the fissures in the rocks means that Alpine plants and plants from as far south as the Mediterranean grow side by side.