effigy mounds

Large earthen monuments built by Native Americans, usually in the shapes of animals.  The purposes of effigy mounds are not well understood, although many contain evidence of burials.  See also geoglyph.

Effigy_mounds_lidarHigh-definition LiDAR image of the Marching Bear mound group, Effigy Mounds National Monument, Harpers Ferry, Iowa. Ca. 300-1100 CE.