Wat Chedi Luang is one of Chiang Mai's most prominent old-city temples, centred on a great chedi whose scale explains the name: luang means large in northern Thai usage.
Chiang Mai's official tourism page says the original chedi was completed in 1481 during the reign of King Mengrai's successors. It was later damaged in the 1545 earthquake, so the structure seen today is a restored and altered historic monument rather than an untouched original.
The same official description points to the ordination hall and its Lanna architecture. Give the chedi and the surrounding halls separate attention, and check current temple notices before relying on fixed opening hours or festival arrangements.