As its name suggests Giants Causeway was built by giants., or one giant to be precise.
Way back in the mists of prehistory, the Irish giant Finn MacCool had a falling out with the Scottish giant Benandonner. Finn built a causeway across the sea to the Scottish coast to allow the two giants to fight. Almost too late Finn realised that Benandonner was much bigger than him.
Finn retired to his home with the Sottish giant in hot pursuit. Finns wife, Oonagh hides Finn in a babys crib. When Benandonner comes looking for Finn, he sees the baby. Reaching the not unreasonabe conclusion that if the baby is so huge, the father will be bigger still, Benandonner turns tail and heads back to Scotland pulling up the causeway in his wake to make sure he cannot be followed.
The very similar basalt columns that exist on the coast at Fingals Cave in Scotland lend even more credence to this supposedly true story.
The Giants Causeway is actually a basalt structure of approximately 40,000 interlocking columns. Most of the columns are hexagonal, although it is possible to find columns with five, seven or more sides.
Scientifically, the columns are the result of volcanic activity. As the molten rock cools, it contracts and cracks appear in the same way they might appear in dried mud.
The causeway was declared a UNESCO World Heritage Site in 1988. There is now a modern visitor and information centre and you may choose to walk down to the causeway itself or take the regular shuttle bus.