Basalt is a volcanic rock which in rare cases like this cools to form giant hexagonal columns. Most columns are 6 sided as the name suggests but 4,5, 7 and 8 sided columns can also be found. The location is Giants Causeway, on the north coast in County Antrim near a town called Busmills (Whiskey aficionados will also recognize this town as being famous for Irish Whiskey). Giant's Causeway Basalt is a World Heritage Site.