The Honeycombs, Giant's Causeway, County Antrim photographed by the Detroit Publishing Company circa 1890-1900. The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic eruption. 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 or eight sides. The tallest are about 39 feet high, and the solidified lava in the cliffs is 92 feet thick in places.