Most of Xi'an's biggest sights are technically day trips — the Terracotta Warriors, Huaqing Pool, and Mausoleum of Qin Shi Huang are 40 km east, easily combined as a single morning–afternoon outing. The Yangling Mausoleum is a quieter half-day to the north.
Further out, Mount Hua (120 km east) and Famen Temple (120 km west) are full-day trips, both reachable by direct high-speed train or bus. The Qianling Mausoleum is often combined with Famen on the same circuit. With longer time, the well-preserved Ming-era walled town of Pingyao is a worthwhile overnight, four hours away by train.