Explanation:

Doon or Dun is a local word for valley, particularly an open valley in the Shivaliks or between the Shivaliks and higher Himalayan foothills. Other valleys in this region have names like Patli Dun, Kotli Dun, Pinjore Dun in Himachal. Such valleys are termed Inner Terai in Nepal.The Doon Valley lies between two intermittent ranges of the Himalayas, the Outer Himalayas and the Lesser Himalayas, know locally as the Mussoorie Range. It is bounded on all sides by mountains, with northern range running from Kalsi in the west to Muni Ki Reti in the east with Mussoorie at the centre in a semi-circular arc; and southern range running at south from Paonta Sahib in the west to Haridwar in the east.