Twin Mounds (conical mounds), Cahokia Mounds Museum.

Featherstonhaugh's 1844 drawing of Monks Mound. Note the small conical mound addition on the west (left with trees) first terrace, and another exagerated one on the summit.

1. Flat-topped mounds.
2. Conical mounds.
3. Ridge-topped mounds (sometimes called boundary mounds).

Mound 72 (a ridge-topped mound), Cahokia Mounds.

Monks Mound could be considered a complex mound which includes one, possibly two conical mound on a flat-topped mound. Before it was leveled in the mid-19th century by the farmer living on top, Monks Mound contained at least one conical mound on the third terrace. A second conical mound is located on the first terrace. Significantly, this conical mound on the western edge of the first terrace is located due north of Mound 72.