Thule as Tile on the Carta Marina of 1539
by Olaus Magnus
In ancient times Thule referred to an unchartered land alleged to be six days travel north of England. The name is commonly credited to Greek geographer Pytheas who between 330 and 320 BC was the first known scientist to sail to the arctic and report perennial polar ice and the midnight sun. While his route remains mysterious and a topic of debate, Pytheas nevertheless introduced the idea of distant Thule to the geographic imagination. Thereafter medieval geographers denoted any faraway place beyond the "borders of the known world" as ultima Thule.