Green Wall is a notorious Class V rapid located at mile 17. 8 on the Illinois River, known for its complex entrance, narrow constrictions, and multiple hazards including boiling holes and tight slots that require expert navigation.

The rapid should be scouted from the left bank before running, and is considered one of the most challenging sections on the river with a reputation for flipping unprepared boats.

This rapid is recommended only for experienced paddlers with proper guide support, as the consequences of error are severe given the river's remote location with no road or trail access for rescue.