Sumatra, is an island in western Indonesia and part of the Sunda Islands. It is the largest island that is entirely in Indonesia (two larger islands, Borneo and New Guinea, are shared between Indonesia and other countries) and the sixth largest island in the world at 480,847.74 km2 (including adjacent islands such as the Riau Islands and Bangga Belitung Islands), with a current population of over 50 million (54 million administratively, as Riau Islands and Bangka–Belitung Islands are included). Its biggest city is Medan with over 4 million in its metropolitan area. - Source: Wikipedia