The world's largest city wall, it has been restored and is 12m high, 18m wide at the bottom, 15m wide on the top, and 13.7km long. Bikes (including two- or three-person models) can be rented for ¥40 per 120 minutes/bike (or ¥80 for a tandem) plus a ¥200 deposit. You can hire one at the top of the South or East gate; you may return it to other stations on the wall (there is one at each of the four main gates), but be sure to verify this before starting your ride, and know that only the south gate is open after 7pm. Bikes will not be rented if there is any chance of rain, because the top of the wall becomes slippery. Check the weather forecast before you buy a ticket to enter the wall. If you want to foot it though, a complete loop of the walls takes 4-5 hours. The landscaped park around the base of the exterior walls and moat also makes for a pleasant stroll and gives a different perspective on the battlements and towers. The wall is lit up at night and makes for a pleasant stroll. The present city wall was built in the Ming dynasty (AD 1368-1644) on the foundation of the Chang'an Imperial city wall of Tang dynasty (AD 618-907). The Xi'an City Wall International Marathon is held each year in November since 1993, with athletes from more than 50 countries running on top of the wall. Also, the Xi'an city wall Cycling Race is held on top of the wall since two years ago. There is a small museum inside the city wall at Hanguang Gate, about halfway between the southwest corner and the South Gate, accessible from the top of the wall. Look for a staircase down inside a covered structure. Inside are the unrestored remains of a gatehouse and a calligraphy collection.