The Three Kings Monument stands at the centre of the old city, in front of the Chiang Mai City Arts and Cultural Centre. Three bronze kings — Mangrai of Chiang Mai, Ramkhamhaeng of Sukhothai, and Ngam Mueang of Phayao — stand in conference, a monument to the alliance that founded the city in 1296. Thais come here to make offerings and the base is frequently garlanded with flowers and incense.
The surrounding plaza is a pleasant open space, with several good museums nearby. The Chiang Mai City Arts and Cultural Centre behind the monument covers the history and culture of Lanna — it's one of the better small museums in the city and an excellent first stop if you want context for everything else you'll see.