Muralla de la Ciudad de Xi'an

Xi'an's city wall, built 1370–1378 on Tang dynasty imperial city foundations, is the most complete surviving ancient city wall in China — 14 km in circumference, 12 metres high, and 15–18 metres wide at the battlemented top. Visitors can walk the full perimeter (3–4 hours) or rent bicycles for a 2-hour circuit above the rooftops of the ancient city.