Malbork Castle

The Castle of the Teutonic Order in Malbork, commonly known as Malbork Castle, is a 13th-century castle complex located in the town of Malbork, Poland. It is the largest castle in the world measured by land area and a UNESCO World Heritage Site.It was originally constructed by the Teutonic Order, a German Catholic religious order of crusaders, in the form of an Ordensburg fortress and named Marienburg in honour of Mary, mother of Jesus. In 1457, during the Thirteen Years' War, the castle was sold by Bohemian mercenaries to King Casimir IV of Poland in lieu of indemnities.

Source: Wikipedia