The Giant’s Causeway is a tightly packed cluster of some 40,000 columns of basalt (a black volcanic rock). It’s located at the foot of a sea cliff that rises ninety meters on the northern coast of Northern Ireland. Although legend says the formation was created by a giant named Finn McCool, it in fact resulted from the volcanic eruption some sixty million years ago, one of a series that brought about the opening of the North Atlantic. The eruption spewed up vast amounts of liquid basalt lava, which cooled to form the columns. They are up to thirteen meters tall and are mainly hexagonal, although some have four, five, seven, or eight sides.