Stretched across diverse picturesque landscape, Nepal lies geographically sandwiched between China and India. Nepal encompasses total surface area of 147,181 sq. km from the Himalayan range in the North to the Indo-Gangetic lowlands in the South at the latitude 26°12′ to 30°27′ North and the longitude 80°4′ to 88°12′. Topographically, Nepal has lowland Terai Region in the south, central lower mountains and hills in the middle and Mountain Region in the north. On the basis of diverse ecological settings, regions have been divided into Terai, Siwalik, Middle Mountain, High Mountain and High Himalaya. Terai lies in the northern part of Indo-Gangetic plain extending nearly 800 km from east to west and about 30-40 km from north to south occupying 17% of the total land area with average elevation below 750 m including Terai region, Bhavar Terai and Inner Terai. Siwalik is also called Churia Hills and has elevation ranging from 700 to 1,500 m. Middle Mountain is also referred as Mahabharat range which stretched on 65% of the total land area with elevation ranging from 1,500 to 2,700 m. Kosi, Gandaki, Karnali and Mahakali river meet the middle mountain at many junctions. High Mountains range from 2,200 to 4,000 m and are naturally resourced with phyllite, schists and quartzite. The soil found here being shallow resist weathering. Where as High Himalayas occupy 16% of the total land area of Nepal with elevation ranging from 4,000 to above 8,000 m. This region accommodates the eight of the highest peaks in the world; Mt. Everest [(8848m], Kanchanjunga [8586m], Lhotse [8516m], Cho Oyu [8201m], Dhaulagiri [8167m], Mt. Makalu [8463m], Manaslu [8163m] and Annapurna I [8091m].
I have nothing more to add except to say its one of the most beautiful treks I have taken!