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The Castle in Malbork (Polish: Zamek w Malborku, German: Ordensburg Marienburg) is the largest castle in the world by surface area, and the largest brick building in Europe. It was built in Prussia by the Teutonic Knights, a German Roman Catholic religious order of crusaders, in a form of an Ordensburg fortress. The Order named it Marienburg (Mary's Castle). The town which grew around it was also named Marienburg.
The castle is a classic example of a medieval fortress, and on its completion in 1406 was the world's largest brick castle. UNESCO designated the "Castle of the Teutonic Order in Malbork" and its Museum as a World Heritage Site in December 1997.
See also: whc.unesco.org/en/list/847