Located in the Haidan District in northwestern Beijing, Purple Bamboo Park is a lovely spot to run and also a particular Beijing experience. The park has 3 lakes (dating back to 1159!) filled with lily pads, and walkways surrounded by bamboo. On an early morning run, you’ll see people practicing Tai chi or singing opera. There are about 5km worth of paths in the park.
There are several important sites in this area, including the National Library, the Capitol Indoor Museum, Banknote Printing and Mint Museum, and just to the east of the park, the Zoo and Aquarium. Subway stops all over.
This can be combined with Yuyuantan (Jade Lake) Park, which is located 3–4km to the south, and has some 6k of trails.