Changbai Shan, China's largest nature reserve, is an area of outstanding natural beauty located in Jilin Province on the North Korean border.
The highlight is Heaven Lake, a spectacular volcanic crater lake which lies at 2194m above sea level and is surrounded by high mountains.
There is also a 68m high beautiful waterfall, a small picturesque lake and many acres of unspoilt forests where Manchurian tigers roam ( although you are very unlikely to see one).
Hiking opportunities abound.
Be aware that one third of the crater lake lies in North Korea, so be vigilant while trekking, don't go too far!