The Giant's Causeway is located in County Antrim, on the northeast coast of Northern Ireland,and is the most popular tourist attraction in Northern Ireland.
The tops of the columns form stepping stones that lead from the cliff foot and disappear under the sea. Most of the columns are hexagonal, although there are also some with four, five, seven and eight sides. The tallest are about 12 metres (36 ft) high, and the solidified lava in the cliffs is 28 metres thick in places.
For more information see:http://en.wikipedia.org/wiki/Giant's_Causeway