The most fun place I found to ride a bike in China: on top of Xi’an’s city walls. Xi’an (where I lived for two years) is unusual in China because the ancient wall around the center city is still intact. They have been modified to allow cars to go through them, but you can go up on the wall and walk all the way around. Or, you can rent bikes and ride all the way around. This was one of the more unique tourist attractions, and I would definitely recommend it!