Seventy percent of its total land area(236,800 square kilometers) comprises mountain and plateau area.The Annamite chain of mountains stretches along part of the border with Vietnam and averages 1,200 meters in height. The mighty Mekong river, one of the longest rivers in the world, flows along the borders with Thailand. The river flows through nearly 1,900 kilometres of Lao territory and has always been a lifeline for the country in terms of fish supplies, transportation routes and agriculture.Several hydro-electric facilities, situated on the tributaries of the Mekong, generate electricity for export to Thailand.