On the Antrim coastline, in North Ireland, you'll find one of the world's most breath-taking geological wonders, the Giant's Causeway. Stretching into the sea are over 40,000 hexagonal pillars formed from volcanic rock thought to be 60 million years old. Legend says that they were built by the giant Finn McCool to help him get to Scotland to fight another giant; let's hope he's not still around today!