The larger circle, named the “Manza” circle has a diameter of 46 meters, and is the largest stone circle found in Japan. A number of reconstructions of Jomon period dwellings have been built around the site. The slightly smaller circle, named the “Nonakado” circle, is 42 meters in diameter and is located around 90 meters away, separated from the “Manza” circle by Akita Prefectural Route 66. Each circle is made from rounded river stones brought from another river approximately 7 kilometers away. Each circle in concentric, with and inner and an outer ring separated by an open strip approximately 8 meters wide. Each circle contains smaller clusters of stone, including standing stones surrounded by elongated stones in a radiating orientation, forming a sundial which points toward the sunset on the summer solstice and allows for calculation of the winter solstice, the vernal equinox and the sun's movements.