Giant's Causeway

The Giant's Causeway lies at the foot of basalt cliffs on the coast of County Antrim, Northern Ireland. The British Geological Survey places its formation at the start of the Palaeogene, about 60 million years ago, when volcanic activity accompanied the opening of the North Atlantic. At the Causeway, lava accumulated in a substantial lake and cooled; contraction as it solidified produced cracks and the distinctive columnar basalt.

The site is known for roughly 40,000 dark basalt columns that extend toward the sea. The columns are mostly polygonal in cross-section, and their regular geometric appearance is a product of the cooling and contraction of lava rather than human construction. The wider coast preserves formations that help geologists study the volcanic events and sequence of landscape development in the region.

UNESCO inscribed the Giant's Causeway and Causeway Coast as a World Heritage property for its geological significance and striking natural features. The basalt columns inspired stories of a causeway built by giants to reach Scotland. The legend is part of the cultural history of the landscape; geological evidence attributes the formation to ancient volcanism.