The park is centered around a stream that flows from Matthiessen Lake to the Vermilion River. The stream has cut partway through the sandstone layers, leaving interesting rock formations and drops. The Upper Dells begin at Matthiessen Lake with the Lake Falls, which drop into the canyon below and continue downstream to the 45-foot-tall Cascade Falls where the Lower Dells begin.
Matthiessen State Park is located a few miles south of the more famous Starved Rock State Park on Illinois State Route 178 just south of Utica, Illinois. Its principal attraction is the mile-long canyon which is nearly 100 feet deep in places and from 50 to 140 feet wide.
It's a well-developed area for hiking and offers a network of staircases and bridges, where visitors can stand and marvel at the beauty not only surrounding them, but far below. In more than one place, the steps lead to the very floor of a gorge where clear, ice-cold water is dotted with stepping stones. Be prepared for mud in many places!
At the end of the Lower Dells, there is a cave with two entrances you can hike through, seen in the photo below...