Most people just fly into Xian, see the terra cotta soldiers and leave,for which they miss a lot. It's like seeing only the Sphinx and being finished with Egypt.
Xian had been the capital of China for over 2,000 years under various rulers/kingdoms. Therefore there are a lot more to see than just the terra cotta soldiers. The Xian provincial museum (30 RMB) is well worth two hours to learn enough history to put the Mausoleum in context. A side trip on the way to the airport would be the newly (02) finished museum housing the burial items (thousands)of Han Jingdi, in which the soldiers are one-third size, along with a large group of civil servants and the entire court; farmers and farm animals, etc. This was an involuntary excavation discovered when they were building the road to airport. Give you a sense of the incredible amount of stuff yet to be uncovered. I would skip the trips to the Buddahist temples and towers (although they are 1,300 years old), unless you are into the religion, and go for the Forest of Stele. The muslim street is worth a trip even if you are squeamish about the food. The muslim population and their wares evokes the Middle East.