That Xieng Teung (Xieng Teung Stupa) is the most important stupa in Muang Sing. It is said to contain the adam’s apple of Buddha. To the left of the stupa are some stairs which lead to a sacred fountain and a sacred stone. If you follow a path to the right of the stupa (be careful!) downhill you might be able to find the old moat and wall of the stupa. The biggest festival of the year, That Xieng Teung Festival, is held here every year during the full moon of the 12th lunar month (usually in late October or early November). The stupa is located 5.5km from the center of town, on the road towards Luang Namtha, situated on top of a hill. A dirt road leads up to it on your right as you’re coming from Muang Sing.
Source: Laos Tourism