Songpan's Ming Dynasty city wall, first built in 1379 and surviving in substantial sections today, is 6.2 kilometres long, 12.5 metres high, and in places 12 metres thick — a scale that reflects the town's historical importance as both a military post and a trade entrepôt. The blue-grey brick, mortared with a mixture of glutinous rice, lime, and tung oil, has held together considerably better than most Ming fortifications of comparable age.
The wall is walkable along its upper rampart, with the best sections accessible from the main gates. The carved stone gateways at each of the cardinal directions are individually designed and worth comparing. The West Gate gives access to the river bank and the covered bridge, and from the rampart above it you can see the valley narrowing into the mountains that Tibetan horse-trading caravans would have entered for weeks of travel.