Wat Phra That Choeng Chum (วัดพระธาตุเชิงชุมวรวิหาร) is located in the center of Sakon Nakhon and is the city's most revered temple. It's history traces back to the 10th century, when a Khmer prang temple was built on the spot. At that time, Sakon Nakhon was a important town of the Khmer Empire of Khotraboon. It is believed that the four incarnations of the Buddha (Phra Kakusantha, Phra Konakom, Phra Kassapa, and Phra Kodom) came here and made footprints in the soil. In the 17th century, the footprints were covered by the 24 meter chedi that we see today — a chedi being a stupa that contains relics of the Buddha, Kings, or important monks.
Wat Phra That Choeng Chum takes on special importance at the end of the rainy season in October, when the Buddhist holiday Wan Ok Phansa (วันออกพรรษา) or "End of Buddhist Lent Day" occurs. Sakon Nakhon celebrates this time with its famous Wax Castle Festival, which features models of shrines, castles, and temples made of bees wax — a meticulous and painstaking process. After a parade of these gorgeous wax models, they are showcased for further view at the temple.
Wat Phra That Choeng Chum is also notable for being home to Luang Por Ong Saen (หลวงพ่อพระองค์แสน), a sacred Buddha statue in the attitude of subduing the demon king Mara, created in the Chiang Saen/Lanna style. It's also interesting to note that the temple's three-story drum tower was built in 1960 by Vietnamese immigrants to Sakon Nakhon, many of whom are Catholic and live in the nearby town of Tha Rae.