Day 01: Gangtok - Lachung Day 02: Lachung - Yumthang- Lachung: Day 03: Lachung - Gangtok Changu Lake Excursion: A Day excursion and back from Changu Lake . Changu Lake with an average depth of 50 ft, is situated at 2 hours drive from Gangtok at the altitude of 3750m. This is on the Gangtok - Nathula Highway , to the Tibet border.