One of the rare places in the world where you'll have an opportunity to glimpse the Siberian tiger in the wild, Changbai Nature Reserve serves as a border between China and North Korea. Access to the park can be had from both the north and south, although, because it is a preserved area, there is no camping and only commercial and maintenance vehicles are allowed.
We suggest catching a charter from the nearby town of Baihe to access Changbai Shan, a volcanic mountain upon which the park's most popular attraction, Tianchi Lake, is situated. Then again, it may be best to join a local tour, which would include the park fees and transportation in up front costs, while also showing you important sights like hot springs, waterfalls, and, of course, the inimitable Tianchi. If you're one to brave the off-the-beaten-path region of the Yunnan Province and explore a diverse mountain ecosystem, then find your way to the Changbai Nature Reserve.
Note:Make sure to avoid circumnavigating the lake, especially on your own, for some of it actually crosses the border into North Korea. Don't say we didn't warn you!