Nepal lies along the mountains of the central portion of the Himalayas. This rectangular piece of South Asia has acted as an important bridge linking two ancient civilizations of the Asian continent – China in the North and India in the South. The land slopes downwards from the almost impenetrable and mighty Himalayan wall of the North until it reaches the Southern fertile Tarai plains. The narrow track of Tarai plains was once covered by thick tropical forest known as the Char Kose Jhadi. This malarial curtain kept settlements out until recently when the forests started being cleared and people from all directions came to settle down, making it the fastest growing habitated area in the country. India lies to the South of the Tarai. The river Mechi flowing from North to South is the Eastern border and the river Mahakali makes up the Western border of Nepal. Nepal was once much more extensive and included the present-day Indian Kumaun and Gadhwal and all the hill country West to the river Sutlej.