Samosir, or Samosir Island, is a large volcanic island in Lake Toba, located in North Sumatra Province. At 630 square kilometres (243 sq mi), Samosir is the largest island within an island and the fourth largest lake island in the world. It also contains two smaller lakes, Lake Sidihoni and Lake Aek Natonang. Samosir is a popular tourist destination due to its exotic history and the vistas it offers. The tourist resorts are concentrated in the Tuktuk area. The island is the centre of the Batak culture and many of the Toba Batak traditional houses (rumah adat) remain on the island