Sado Island Off the West Coast of Honshu, Japan38.0N 138.3E
Sado Island is visible in the Sea of Japan off the coast of Honshu, the main island of Japan, northeast of the Noto Peninsula. The peninsula is part of Ishikawa Prefecture, while Sado Island is part of the Niigata Prefecture.
Since 2004 the city of Sado has comprised the entire island of Sado, although not all of its total area of 855.26 km2 is urbanized. Sado is the sixth largest island of Japan in area following Okinawa Island and excluding the Northern territories.
The island consists of two parallel mountain ranges running roughly southwest-northeast, enclosing a central plain. The Ōsado Range, in the North, is slightly higher, with peaks including Mount Kinpoku, the highest point of the island at 1,172 m, Mount Myōken, and Mount Donden. The Kosado Range in the South faces the Honshū coast. The highest point in Kosado is Ōjiyama at 645 m.
The plain in between those ranges is called Kuninaka and is the most populated area. The Kuninaka plain opens on its eastern side onto Ryōtsu Bay, and on its western side onto Mano Bay, where the island’s longest river, Kokufugawa (or Konogawa) reaches the sea.