Much of the country's land area has been built up from alluvial deposits brought down by the major rivers. The land is mostly flat except for a range of hills in the south-east. Wooded marshylands and jungles mainly characterize it with forest regions in Sylhet, Rangamati, Khagrachari and Bandarban Hill Tracts, Sundarbans, Mymensingh and Tangail. The history of Bangladesh has been one of extremes, of turmoil and peace, prosperity and destitution. It has thrived under the glow of cultural spiendour and suffered under the ravages of war.
Evidence also suggests that there was a strong Mongoloid presence as well.
Soon after, in the 5th and 6th centuries B.C. came the Aryans from Central Asia and the Dravidians from Western India. Then came the Guptas, Palas, Senas, who were Buddhist and Hindus. From the 13th century A.D. the flood of Muslim invaders and the tide of Islam swamped the Buddhist and Hindus untold 8th century. Sometimes there were independent rulers like the Hussain Shahi and Ilyas Shahi dynasties while at other times they ruled on behalf of the imperial seat of Delhi. British political rule over the region began in 1757 A.D. when the last Muslim ruler of Ben.