Ancient earthen structures in Ohio become a UNESCO World Heritage Site

This is fabulous! There are so many sites that have been taken apart or plowed over, however, there are many still present and if people dig around, they can find. It is not known for sure when some of them were built. They or huge structures from shells and earth are all the way from San Franciso to the East Coast in America and into Canada down into South America! Many sites there is not much if anything known about them. It is a positive thing though to realize that the Americas had highly developed peoples on many levels. I just want to add that making structures does not mean people are more intelligent than those who did not.