Changu Lake, Sikkim
Changu Lake, also called Tsomgo lake rests at an altitude of 12000 ft above sea level. This is on the way to Nathula Pass which is also the India-China border. Given the altitude and climate, fall is the most beautiful thing that could have happened to this region. The colourful prayer flags add to aesthetic beauty of the Changu lake surrounded by Alpine/ Sub alpine vegetation.
The local religion Buddhism is very rampant and Changu lake has many prayer flags on its banks indicating its religious importance to the locals.
Getting there: You would need to hire a jeep with driver. Wouldn't suggest driving the Himalayan ghats to novices. Opt for a air conditioned vehicle. Given the steep ramp drive, vehicles are bound to emit a lot of diesel smoke.
Acclimatising: Probably talked about in every opportunity, but it definitely deserves its importance and is not a bit over rated. Your local driver would suggest stopping at intervals to acclimatise to the altitude. As the saying goes, Take Deep Breaths and Be Alive!