I like pottering around the old part of Chiang Mai on Sundays. Not only is it full of nice cafes and shops but some of the oldest and most interesting temples lie here as well. I like walking around the spacious Wat Chedi Luang compound (if it's not too hot - the best time to go is before 11 am or after 4 pm). The name literally means 'Royal Pagoda' and for a time the Emerald Buddha was housed here before being moved to Bangkok. The Chedi was built almost 600 years ago and was partly destroyed, whether by an earthquake or during the Burmese invasion in the 18th Century is uncertain.
Wat Chedi Luang lies in the heart of the old city on Prapokklao Road, close to the Prapokklao-Rachadamnoern Road intersection. It's easy to find and close to several other temples as well. On Sunday evenings the Walking Street Market or 'Thanon khon deuhn' is held on this street too and remains my absolute favourite of all Chiang Mai markets.