The Castle of the Teutonic Order in Malbork, Poland, is the largest castle in the world measured by land area. Covering approximately 143,591 square meters (over 35 acres), this 13th-century brick Gothic fortress was the headquarters of the Teutonic Knights. It is a UNESCO World Heritage site and is remarkably well-preserved despite heavy damage during WWII. While other structures like the Prague Castle or Windsor Castle are often cited for their continuous royal residence or sheer volume, Malbork's sprawling outer, middle, and high castle complexes make it the undisputed champion of total footprint. In 2026, it remains a major cultural hub in Poland, offering visitors a grounded look at medieval monastic and military power through its massive brick walls and intricate vaulted chambers.