The Dooars or Duars are the alluvial floodplains in northeastern India that lie south of the outer foothills of the Himalayas and north of the Brahmaputra River basin. This region is about 30 km (19 mi) wide and stretches over about 350 km (220 mi) from the Teesta River in West Bengal to the Dhansiri River in Assam. The region forms the gateway to Bhutan. It is part of the Terai-Duar savanna and grasslands ecoregion. There are 18 passages or gateways between the hills in Bhutan and the plains in India. This region is divided by the Sankosh River into Eastern and Western Dooars, consisting of an area of 880 km2 (340 sq mi).