After an extended trek through the Forbidden City, what we need is a tranquil place to rest and regroup. Luckily, the beautiful Beihai Park is just northwest of the palace complex. We'll stroll along peaceful pathways, admire the temples and pavilions, and enjoy the unusually serene scenery. Around what type of geological formation is Beihai Park centered?
A canyon
A lake
River rapids
An extinct volcano