Designated a UNESCO World Heritage site in 1986, the Giant's Causeway in County Antrim, Northern Ireland, is made up of some 40,000 black basalt columns that resemble a haphazardly built staircase. Folklore holds that legendary hero Finn MacCool plunged the columns into the sea to create a bridge to Scotland, but scientists say that volcanic activity shaped the causeway's rock formations 65 million years ago. Take a tour with the photo gallery above.