How can I make the best use of 2.5 days in Xian?

Hi guys,

I will spend 2.5 days visiting and back to Beijing to catch the flight back. My plan is traveling to Terracotta Warriors on 1st day and Qianling Museum, Ancient City Wall on 2nd day. I wonder where I can go on the rest half day. Is City Museum okay? Please suggest some other beauty spots.

Thank you~