<P> Bowl - or saucer - shaped, Cambodia covers 181,035 km (69,898 sq mi) in the south - western part of the Indochinese peninsula as its landmass and marine territory is situated entirely within the tropics . </P> <P> The bowl's bottom represents Cambodia's interior, about 75 percent, consisting of alluvial flood - plains of the Tonlé Sap basin, the lower Mekong River and the Bassac River plain, whose waters feed the large and almost centrally located wetlands . As humans preferably settle in these fertile and easily accessible central lowlands, major transformations and widespread cultivation through wet - rice agriculture have over the centuries shaped the landscape into distinctive regional cultivated lands . Domestic plants, such as sugar palms, Coconut trees and banana groves almost exclusively skirt extensive rice paddies, as natural vegetation is confined to elevated lands and near waterways . The Mekong traverses the north to south - east portions of the country, where the low - lying plains extend into Vietnam and reach the South China Sea at the Mekong Delta region . </P> <P> Cambodia's low mountain ranges - representing the walls of the bowl - remain as the result of only rather recent substantial infrastructural development and economic exploitation - in particular in remote areas - formidably forested . The country is fringed to the north by the Dangrek Mountains plateau, bordering Thailand and Laos, to the north - east by the Annamite Range, in the south - west by the Cardamom Mountains and in the South by the Elephant Mountains . Highlands to the north - east and to the east merge into the Central Highlands and the Mekong Delta lowlands of Vietnam . </P> <P> A heavily indented coastline at the Gulf of Thailand of 443 km (275 mi) length and 60 offshore islands, that dot the territorial waters and locally merge with tidal mangrove marshes - the environmental basis for a remarkable range of marine and coastal eco-regions . </P>

Landform that separates vietnam from cambodia and laos