Built in the 13th century, Marienburg, a fortress of the Teutonic Order, is located on the River Nogat in Poland. Between 1309 and 1454, it served as the seat of the grand master in the state of the Teutonic Order. The order was established in the 12th century during the Third Crusade, and ruled over extensive territories in the Baltic region between 1230 and 1561. These included territories between the Vistula and Memel rivers that subsequently became West Prussia and East Prussia, as well as up to 1561 large parts of present-day Estonia and Latvia.
The Teutonic Fortress of Marienburg, colour photograph, 2010, photographer: DerHexer; image source: Wikimedia Commons, Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 Unported (CC BY-SA 3.0).