Within the Park is the Phimai Sanctuary, one of the grandest and most important Khmer historical sites in Thailand. The word Phimai appears in an inscription on a stone slab at the front doorway of the building as well as in many other structures. It is believed that the word Phimai referred to a religious figure or site.
The Phimai Sanctuary is rectangular in shape and is 565 meters wide and 1,030 meters long. It consists of ornately carved sandstone and laterite structures. The most special characteristic of the sanctuary is that it is the only one that faces south while the others usually face east. This is probably because it was built to face the route that the Khmers traveled from the capital of the empire, to the south of Phimai.