The old city of Chiang Mai is defined by a square moat about 1.5 kilometres on each side, built by King Mangrai in 1296. Inside the moat are the majority of Chiang Mai's important temples, several small museums, and most of the budget guesthouses and cafes. The walls and gates have been partially restored and make for a pleasant circuit on foot or by bicycle.
The grid of streets inside the moat is quiet enough that you can wander without a plan — turning down an unmarked lane often reveals a small temple, a traditional wooden house, or a neighbourhood market. The old city is compact enough that everything within it is walkable, and staying inside the moat puts you within reach of all the main sights.