Hengill, Iceland - Hengill was formed from a Palagomite tuff, it is a central volcano and has a giant magma chamber beneath it. When thick basalt lava flows cool, they form hexagonal cracks, called columnar joints
Cahir Castle is one of the largest castles in Ireland, and is sited on an island in the River Suir. It was built in 1142 by Conor O'Brien, Prince of Thomond. In 1961 the last Lord Cahir died and the castle reverted to the Irish State.