At the top of a hill a short distance from the northwest corner of Chiang Saen is the temple of Wat Phrathat Chom Kitti. The temple, and in particular its chedi, is thought to pre-date the founding of Chiang Saen.
You can reach the the temple via a stairway of 350 steps from the main road at the base of the mountain, or you can be lazy and drive up. Either way, look out for the many statues seemingly placed randomly in the forest of teak trees which cover the mountain. Many formal gateways mark the stairway up.