The What Do We Know About? series explores the mysterious, the unknown, and the unexplained.  Was the Giant’s Causeway really built by giants? Learn all about the mystery surrounding one of the United Kingdom’s greatest natural wonders.The Giant's Causeway is a spectacular geological formation in Northern Ireland that is a popular tourist destination and UNESCO World Heritage Site. According to Irish folklore, in the third century, a giant named Finn McCool was challenged to a duel by another giant in Scotland. In this legend, Finn accepted the challenge and built a path across the North Channel, anxious to face his foe once and for all. Was this how the Giant’s Causeway was created? Or have science and geographic studies explained the hexagonal stone columns as the result of an ancient volcanic eruption? Find out everything we know about this mysterious geological rock formation steeped in myth and folklore.