A stone circle was constructed mainly in the eastern part of Japan in the Late Jomon sub-period (1,500-1,000 BC). The Nishizakiyama stone circle is located at the top of Mt. Nishizakiyama (70 m) in Yoichi Town in Hokkaido. As a precious ruins place of a stone circle constructed about 3,500 years ago, it is prefecturally designated as a Historic Site.

In Nishizakiyama ruins, stones about the size of a human head are placed in circle with a stone pillar erected in the center. Pieces of Middle-Jomon earthen ware and the pit holes of 50 cm in diameter and 70 cm in depth were discovered from under the stones. As phosphor was detected in the holes, this place is supposed to be the burial ground.