It is bounded by (from the north and clockwise) the districts of Ammerland, Oldenburg, Vechta, Osnabrück, Emsland and Leer.In terms of political history, both Cloppenburg and neighbouring Vechta are, as one of the few historically Catholic districts in an otherwise majority-Protestant state, some of the most conservative areas in Germany.The district, alongside neighborging Vechta, have due to their large Catholic population the highest birth rates and lowest median ages in Germany.[3][4] The district comprises the western portion of a historical region called Oldenburgisches Münsterland, which means "lands of Oldenburg formerly held by Münster".The Thülsfelde Reservoir is an artificial lake that was built between 1924 and 1927 in order to prevent floods in the area.