The Cathedral Basilica of Our Lady of Amiens (French: Basilique Cathédrale Notre-Dame d'Amiens), or simply Amiens Cathedral, is a Roman Catholic church. The cathedral is the seat of the Bishop of Amiens. It is situated on a slight ridge overlooking the River Somme. The cathedral was built almost entirely between 1220 and c. 1270, a remarkably short period of time for a Gothic cathedral, giving it an unusual unity of style. The cathedral has been listed as a UNESCO World Heritage Site since 1981.