Northern Ireland, Part II (Giants Causeway and the South) This episode starts at the most visited site in Northern Ireland, The Giant’s Causeway. It’s a dramatic coastal landmark that draws visitors from around the world. Then it’s off to the historic city of Londonderry, on the banks of the Foyle River. From there we head underground at the Subterranean National Park, before putting on an apron for a lesson in Irish cooking.