What type of physical features did the mound builders lived?

east of the mississippi

The Mound builders' lived in ceremonial structures which are typically platform mounds or flat-topped pyramids, elongated ridges, rounded cones, and some varieties of other forms that were basically constructed as the complex villages.

According to archaeology of North America, "Mound builders" is the name that refers those people who construct mounds in a vast area ranging from the Great Lakes to the Gulf of Mexico and from the Mississippi to the Appalachian. The best concentrations of mounds are seen in the Ohio valleys and Mississippi river.

well this isn't a question but if you are asking if it is true or false it is, true.