Cahokia Mounds
noun
a group of very large prehistoric Indian earthworks in southwestern Illinois, consisting of mounds with flat tops that supported temples and other structures of mud and thatch.
British Dictionary definitions for cahokia mounds
Cahokia Mounds
/ (kəˈhəʊkɪə) /
pl n
the largest group of prehistoric Indian earthworks in the US, located northeast of East St Louis