It is a wonderful site, not doubt about it. However, if you have limited time in China, probably pick Beijing, Yangtze River Cruise, Shanghi, and Yangshuo.
The Terra Cotta Warriors are really interesting. The Number 3 building was the most interesting and just as interesting as the Number 1 Building.
This site gets so much hype; but do not believe it merits one of the world's best as many other reviews have stated.
Would really recommend Shanxi, Shuhe, and Lijiang as a must go before going to Xian to really see this one site. If you have limited time and money this would be on a subsequent site visit list. More