Malbork (mälˈbôrk) [key], Ger. Marienburg, town (1994 est. pop. 40,100), Pomorskie prov., N Poland, on the Nogat River. It is a rail junction with sugar refineries and dairies. Originally a castle founded (1274) by the Teutonic Knights, Malbork became the seat of their grand master in 1309. It successfully withstood sieges by the Poles in 1410 and 1454, but in 1457 Malbork was sold to Poland by mercenaries whose pay was in arrears. The town passed to Prussia in 1772. Germany took control of the town in 1920, and it was returned to Poland in 1945. The castle (rebuilt in the 14th and 19th cent.) is one of the finest examples of German secular medieval architecture.