there`s no such thing as Mound Builders & NEVER was, they`re all collapsed structures etc or corpses of giant animals or humanoids / mud fossils.
...
https://www.youtube.com/watch?v=4bCWhWeb3MM
M`t Nemrut has eroded in a way that it must be this side of the flood or was used as a quarry for lime production for concrete mixes, if so the entire area for miles looks the same and so could have been an entire city sized metropolis of huge tall buildings.
...
https://www.youtube.com/watch?v=rJXMkWZpxeA