The beautiful hill station, Gangtok is placed in the lower Himalayas at an altitude of 5,500 ft (1,676 m). Roro Chu and Ranikhola are the two streams by which the city is flanked. These two rivers bifurcate the natural drainage into two parts, the eastern and western parts. The two streams before joining the powerful river Teesta at Singtam meet at the Ranipul and flow south as the main Ranikhola .

Gangtok, is underlain by Precambrian rock. Landslides are a common feature here. According to the Bureau of Indian Standards, the town comes under seismic zone-IV adjacent to the the convergent boundary of the Indian and the Eurasian tectonic plates. It is also prone to frequent earthquakes as well. The town is enveloped by the snow-covered Himalayan ranges from distance. To the western part of the city ,Mount Kanchenjunga (8,598 m or 28,208 ft) is visible.

Gangtok is nestled amidst thick forest. Some of the important forests are temperate, evergreen and deciduous forests. The hill town has numerous rare varieties of orchids. Bamboos are also stuffed. In the lower region, the vegetation shows changes from alpine to temperate deciduous and subtropical. The hill town blooms with a wide variety of flowers namely sunflower, marigold, poinsettia etc.