It spreads out in a valley at an altitude of about 480m to 530m on the mountainside of Mt. Une (699m above sea level), the highest peak in Mihara City. The huge granite boulders, with diameters of 1 to 7m, are called "Gouro" and you can enjoy the impressive scenery of their undulating accumulations. The area of ​​about 22 hectares is about 10 times the size of the old Hiroshima Municipal Baseball Stadium, and its scale is overwhelming.

Geologically, it is thought that the rock core (core stone) that was left behind by groundwater seeping in along the cracks (joints) of the granite and weathered decomposed soil flowing out in an onion shape accumulated in the valley. "Mineoto Gorge" is a mysterious spot where you can hear the sound of groundwater flowing under the sea of ​​rocks through the gaps in the rocks, and it is not clear where it flows from.