The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic eruption.
It is located on the northeast coast of Northern Ireland, about 3 miles from the town of Bushmills, Co. Antrim.
It was declared a World Heritage Site by UNESCO in 1986.
The tops of the columns form stepping stones that lead from the foot of a cliff and disappear under the sea.
Most of the columns are hexagonal, although there are also some with four, five, seven or eight sides.
The tallest are about 12 metres (39 ft) high, and the solidified lava in the cliffs is 28 metres thick in places.
Reference: http://en.wikipedia.org/wiki/Giant's_Causeway