The ruins of Muang Sing beside the Khwae Noi River date from around the 13th century and mark the westernmost point of expansion of the Khmer Empire. Earthen ramparts surround an inner wall of laterite that forms a rough rectangle about 245 acres (1 sq km). Near the center of this are the ruins of the Buddhist sanctuary, Prasat Muang Sing. Like most Khmer temples it faces east, in alignment with the city of Angkor.
Although the Muang Sing temple complex looks Khmer, some art historians believe it was actually built by local artisans in imitation of the occupying Khmers – the sanctuary, for example, lacks the stylistic details that are normally associated with Khmer sites. It was probably built after the reign of Jayavarman VII (1181–1220) as the Khmer Empire began to decline and its power in this region was fading. A museum at the site displays artifacts excavated here.
Southeast of Muang Sing is Ban Kao, a prehistoric settlement discovered in the 1940s by Dutch archaeologist van Heekeren, a prisoner on the Burma-Siam Railroad. The Ban Kao Museum houses stone tools and ornaments.