The Ross Trails Adena Circle is an archaeological site in the southwestern part of the U.S. state of Ohio. Located northwest of Ross in Butler County, it appears to have been a sacred circle constructed by people of the Adena culture. The circle is composed of an earthen wall, approximately high. Its interior, which is slightly raised above the surrounding terrain, can be accessed through a small opening in the wall that appears to have housed a gate at one time. Because the circle has never been excavated, its contents and uses are uncertain; however, archaeologists have speculated that postholes or other evidence of a house or similar structure may be contained within the circle. In 1975, the circle's archaeological value was recognized when it was added to the National Register of Historic Places. The landmarked area includes approximately of land, due to the possibility of finding related artifacts in the close vicinity of the circle. References Adena culture Archaeological sites in Ohio National Register of Historic Places in Butler County, Ohio Archaeological sites on the National Register of Historic Places in Ohio