The Giant Causeway is the Antrim plateau in Northern Ireland. Around 60 million years ago, there was an intense volcanic activity in County Antrim which led to the formation of a 3,800 square kilometre lava plateau which now represents the largest lava field in Europe. The lava plateau cooled forming a polygonal network of 40,000 blocks of layered black basalt rock.
The unique characteristic feature of the site is that it has around 40,000 large, polygonal columns of basalt in horizontal sections. The tops of the columns are like stepping stones that lead from the cliff and disappear into the sea. The columns are hexagonal, but you can also find some with four, five, seven, or eight sided blocks.
The tallest block is about 12 metres (39 ft) high, and the solidified lava is 28 metres (92 ft) thick in places. These columns contributed to the development of the earth and it also became the centre of the 18th-century geological debate related to the origins of igneous rocks.
Ancient myths and legends speak of an Irish warrior named Fionn mac Cumhaill who built the causeway so he could walk to Scotland to fight the giant named Benandonner.
The Giant Causeway was declared a World Heritage Site by UNESCO in 1986, and was declared a National Nature Reserve in 1987. The Causeway Coast now receives over 400,000 visitors per year and it has been Northern Ireland's most popular tourist attraction for 300 years.
A 2005 poll of Radio Times readers ranked the Giant Causeway as the fourth greatest natural wonder in the United Kingdom.