Ultima Thule is said to be a distant northern place located beyond the known world. In classical European literature and cartography at various times it has been placed in Norway, other parts of Scandinavia, Iceland, Greenland, into the Celtic world of Ireland, the Western Isles of Scotland and Orkney and Shetland. It was Pytheas, the Greek explorer who was the first to have written of Thule, in his lost work On the Ocean, about his travels between 330-320 BC.