Sadakyo Stone Circle is the generic name for several alignments almost with the same height as a man located in Ajimu-machi-Sada area, Sada City, Oita Pref. It is unknown by whom and for what purposes these stone circles were built. According to one explanation, those stones were built for ancient ceremonies. Another goes they were the antetype of torii, and still other goes that they were the stone marker of the place where mantras were buried. The huge stones are found in several places around Mt. Komekamiyama, which has an altitude of 475 m. As is seen in the name of “Komekamiyama (rice god mountain)” or “Koshiki-ishi (rice-steamer basket stone)” there are many place names with the word concerning rice in this area, from which fact some say these huge stones may have bee built in the Yayoi period, when rice crop started in this country. Copied mantras were excavated from under some stones. The petroglyph letters, which are considered to have been carved by ancient people, were also found. These huge stones are wrapped in mystery including a legend of stones hailing from the heaven.