Prague Castle (66,761 m²)
According to the Guinness Book of World Records, "Prague Castle, is the largest coherent castle complex in the world, with an area of almost 70,000 m²". Build in the 9th century the fort was turned into a royal palace by King Ottokar II of Bohemia in the 13th century. The complex holds 4 palaces and 4 churches amongst various other buildings, towers, walls and gardens.
Nowadays the official office of the President of the Czech Republic houses here. In a hidden room somewhere else in the castle, the Bohemian Crown Jewels are stored. They are a reminder of the old Bohemian Dynasty that once ruled these grounds.
The facade alone measures half a kilometre, so be sure to wear your walking shoes, or take a virtual tour instead!