I have a 10 hour layover in Guangzhou Baiyun Airport.

Sure! You can pay a quick visit to the downtown area. Take metro line 3 from CAN to Jiahewanggang Station, and switch to metro line 2 to Haizhu Square Station. The metro ride takes about 40 minutes, and the fare amounts to CNY7 totally. Then, you can see the Haizhu Square, Beijing Road Pedestrian Street, Pearl River, and Canton Tower. Remember to return to CAN at least 2 hours prior to deprature time. Have fun! ;)