Malbork Castle

MAn hour outside of Gdansk is one of the treasures of Polish history going back to the Middle Ages--Malbork Castle. First built by the Teutonic order to serve as a residence for the Crusaders imposing Christianity on this part of the world, it later became the residence of Polish monarchy.  Much of ot was destroyed during WWII and has been restored over the ensuing decades.  It's become a World Heritage site and justifiably so.