It’s not surprising that there are more than 10 museums in Xi’an and its surrounding areas, since it has a history of more than 2000 years.
If you have time for visiting only one museum, then go to the Shaanxi History Museum. According to Wikipedia, it is one of the first huge state museums with modern facilities in China and one of the largest. The museum houses over 370,000 items, including murals, paintings, pottery, coins, as well as bronze, gold, and silver objects. The modern museum was built between 1983 and 2001 and its appearance recalls the architectural style of the Tang Dynasty.
My friend wrote up a list of museums in Xi’an and its surrounding areas (in Chinese), check it out if you’d like to visit them: https://www.zhihu.com/question/23600587
