The chief attraction of Tokyo’s Marunouchi district is the Imperial Palace with its beautiful 17th-century parks surrounded by walls and moats. Still in use by the Imperial family, the Imperial Palace stands on the site where, in 1457, the Feudal Lord Ota Dokan built the first fortress, the focal point from which the city of Tokyo (or Edo, as it was then) gradually spread. As famous as the palace is the Nijubashi Bridge leading to its interior, a structure that takes its name (“double bridge”) from its reflection in the water. Other notable features include the two-meter-thick wall surrounding the palace and its gates, one of which leads to the East Higashi-Gyoen Garden, one of the few areas open to the public (the main Palace Gardens are only open twice a year, on January 2nd and April 29th, when crowds flock here to catch sight of the Emperor). One fortress that can be visited is Edo Castle (Chiyoda Castle), built in 1457 and located in Tokyo’s Chiyoda district.