The ancient site is on the grounds of the former Hishima Elementary School. Prayer rituals for the safety of ships and sailors were held here during the Nara and Heian periods (8th to 12th centuries).
In 1962, a buried trove of bronze mirrors, copper bells and earthenware was discovered by chance on the school grounds. It included items typically used in religious rituals, such as a small Nara-sansai tricolor ceramic jar, coins, and miniature earthenware vessels, which had been placed around the base of a large rockface. The ritual items were presumably brought from the capital cities of the time (present-day Nara and Kyoto).
Researchers believe the site may have been used for one of the key rituals of the Imperial Court during those eras, praying for safe journeys for the periodic Japanese missions to Tang China. The relics excavated from the site are exhibited at the Kasaoka Folk Museum.