Wat Umong
One of the most unusual temples in Chiang Mai, Wat Umong dates from 1296 and is set in a forest near Chiang Mai University—this style of temple is usually far from urban areas and hard to access. According to local lore, a monk named Jam liked to go wandering in the forest. This irritated King Ku Na, who often wanted to consult with the sage. So he could seek advice at any time, the king built this wat for the monk in 1380. Along with the temple, tunnels were carved out and decorated with paintings, fragments of which may still be seen. Beyond the chedi is a pond filled with hungry carp. If you come early enough in the morning you might see people on mediation retreats clad in white doing their walking meditation around the vast property. Throughout the grounds the trees are hung with snippets of Buddhist wisdom such as "Time unused is the longest time."
Within the Old City is a small temple with the same name. For the larger Wat Umong, tell your driver you're going to Wat Umong Thera Jan.