China is a vast country with many things to see and do. If you only have ten days, we recommend at least visiting Beijing, Xi'an, Guilin and Shanghai. Each of these cities has a different focus, so you could spend a day or two in each one.
In Beijing, you could visit the Great Wall of China, Tiananmen Square and the Forbidden City. You could also go shopping in one of the many markets or malls.
In Xi'an, you could visit the Terracotta Army, the City Wall and the Muslim Quarter. You could also take a day trip to see the pandas at the Chengdu Research Base of Giant Panda Breeding.
In Guilin, you could go hiking in one of the many mountains or forests, go kayaking on the Li River or visit one of the caves.
In Shanghai, you could visit the Bund, Yu Garden and the Shanghai Tower. You could also take a day trip to Hangzhou to see the West Lake.