Having spent a few days doing all this, there is also, of course, the Terracotta Army, which is easily reachable by bus from Xian centre in an hour. Leave a whole day for the Army, as it’s quite a sight to behold building up to the largest excavation, which is the size of a few aircraft hangers.
You can then spend your night dancing away in the largest fountain and lights show in the world. It’s pretty simple; they turn on a lot of fountains, put some Hollywood style red carpet beam lights on, play loud classical music and everyone dances around in the fountains for half an hour every night at 9pm. Not to be missed. But take a change of clothes. Best of all…it’s free!
Leave two or three days for Xian, it’s well connected to Beijing and Shanghai by train and flights but you will need to book ahead in peak season. However, once you get there and see everything Xian has to offer, you may not be in that much of a hurry to leave.