What do the mounds look like?

Mounds are great hills of earth made by human hands. They can be round with broad, flat tops, cone-shaped, or in the shape of animals (Marsh). Mounds range in size from the Serpent Mound (Adena), which is the largest effigy mound in the United States to a Hopewell mound in Warren county, at Fort Ancient, that is 3 Ω miles long. Some Hopewell mounds were found as tall as 7 story buildings. 

The Adena mostly built cone-shaped mounds to bury their dead and artifacts. These cone-shaped mounds were different sizes. Thousands of these type mounds were in the Ohio River Valley.

A Hopewell mound was either an effigy type mound or one built in a geometric shape like a circle, square or rectangle. These mounds were made of earth and clay that had to be carried to the mound site.