Giants Causeway (Ireland)

An area of about 40,000 interlocking basalt columns, the Giants Causeway is a result of an ancient volcanic eruption. Located on the north-east coast of Northern Ireland, most of its columns are hexagonal, although there are also some with four, five, seven and eight sides. The tallest are about 12 meters (36 ft) high, and the solidified lava in the cliffs is 28 meters thick in places. In a 2005 poll of Radio Times readers, the causeway was named as the fourth greatest natural wonder in the United Kingdom.