Khao Kha Archaeological Site in Tambon Sao Phao. To get there, take Highway No. 401 from Si Phibun intersection to the 99-km marker, and turn left onto Chinda Pracha Sawan Road for 7 kilometres. Khao Kha was a sacred religious place of the Sawai Nikai Brahman sect who worshiped Shiva as their highest god.
Khao Kha was regarded as being similar to the mythical Khao Phra Sumen, a centre of worship, that was surrounded by smaller, secondary historical sites. Many artifacts that were used in rites have been found here, including phallic symbols, holy water pipes, ruins, and an ancient pond. The site dates from the 8th-9th century. The Fine Arts Department completed its renovation in 1997.