Nijō Castle is a flatland castle in Kyoto, Japan. The castle consists of two concentric rings of fortifications, the Ninomaru Palace, the ruins of the Honmaru Palace, various support buildings and several gardens. The surface area of the castle is 275,000 square metres, of which 8,000 square metres is occupied by buildings. It is one of the seventeen Historic Monuments of Ancient Kyoto which have been designated by UNESCO as a World Heritage Site.