The northen plains are among the most densely populated regions of the world.These plains are located to south of the Himalayas.They lie almost parallel to the Himalayas. Extending from Punjab in west to Assam in the east,the plains stretch over a lenght of 2,400 km and about 150 to 300 km wide. They cover the states of Punjab, Haryana , Uttar Pardesh, Bihar west Bengal and part of Assam