Flexi Says: Although geologists describe the origin of Giant's Causeway as being the result of basaltic volcanism, the Irish legend states that the giant Finn MacCool built the causeway to meet the Scottish giant Benandonner in battle. Hence the name, Giant's Causeway. Giant's Causeway is composed of more than 40,000 basalt columns. The columns are mostly hexagonal, although they have between four and eight sides. On Scotland, across the Irish Sea, is the other side of the same basalt flows. This connection may have been the origin of the legend of the giants.