Doi Suthep is a mountain, about 15 kilometers from Chiang Mai, with on it Wat Prathat Doi Suthep, a Holy Temple. The place can easily be reached from Chiang Mai. I would say that it is hard not to find a bus or car that wants to bring you there.
It's one of the most well known temple is Doi Suthep located on a 1676 high mountain, close to the city Chiangmai