Northern Ireland’s top tourist attraction, the Giant’s Causeway is a geological formation that looks like it belongs on another planet. (Indeed, in 2009, similar columnar basalt formations have been found on Mars! See this Nasa report.) The bizarre, honeycomb rocky structure sits beneath the dramatic sea cliffs of the north Antrim coast. It consists of around 40,000 polygonal basalt columns protruding from the sea. Most of the column tops have a hexagon shape, though some are octagons, and some have five, seven, nine or more sides. Of varying heights, the tallest column stands at around 39 feet / 12 metres high. The tops of the columns form natural stepping-stones that lead outwards from the cliffs and eventually disappear under the sea. The Giant's Causeway was designated Ireland's first World Heritage Site by UNESCO in 1986 Visitors can walk directly out onto the rocks. There is no fee for visiting the Giants Causeway. There is, however, also a visitors centre (fee required) if you want to find out more.
Nice amateur video showing what to expect when you get to the Giants Causeway
How The Giant's Causeway Was Formed
Geological studies suggest the rock formation was caused by volcanic activity around 50–60 million years ago. Extremely hot molten basalt flowed through the regions chalk beds. As this lava cooled, it contracted and fractured, similar to the the way hot mud fractures when it is cooled. The cracks left the standing pillars, which became more prominent with the erosion of surrounding chalk bed over time.
The Giant's Causeway in Irish Mythology
On seeing this other-worldly landscape, you understand why it has long featured in Irish myth and folklore. An ancient legend, passed on since pre-Christian times via the oral tradition of storytelling, tells that the rocks are the work of the giant Finn McCool. One version of the story goes that McCool built a highway to reach his sweetheart in the Scotland island of Staffa. Another version of the story has it that McCool built the road to challenge a rival Scottish giant known as Benandone.
The Giant's Causeway. Image by Chris Lofqvist