Xi'an is one of the few cities in China where the imposing old city walls still stand. Built in 1370 during the Ming dynasty, the magnificent 12m-high walls are surrounded by a dry moat and form a rectangle with a perimeter of 14km. Most sections have been restored or rebuilt, and it is possible to walk the walls in their entirety in a leisurely four hours (or around two hours by bike, or at a slow jog).
You can cycle from the South, North, West and East gates, with rental costing ¥45 for 100 minutes (¥200 deposit), while the truly lazy can be whisked around in a golf cart for ¥200. Access ramps are located inside the major gates, with the exception of the South Gate, where the entrance is outside the walls; there's another entrance inside the walls beside the Forest of Stelae Museum. En route, you get to look out over modern-day Xi'an. From this vantage point it's clear that the city is a hotchpotch of the old and new, with the new vastly in the ascendancy. Every now and then a slice of old Xi'an, such as Guangren Temple, appears and you are rewarded with a bird's-eye view.
To get an idea of Xi'an's former grandeur, consider this: the Tang city walls originally enclosed 83 sq km, an area seven times larger than today's city centre.
Buses 4, 15 and 201 reach the West Gate; buses 9, 26 and 37 and Line 2 of the metro reach the North Gate; buses 11, 16 and 23 and Line 2 of the underground can get you to the South Gate; and buses 8, 22 and 33 go to the East Gate.