Waterfall Glen is a forest preserve surrounding Argonne National Laboratory. A good access point is S of I55 at the Cass Avenue exit. Turn right at the second road immediately south of the highway. At this parking lot and in a few other locations are maps of the forest preserve with some trail distances shown. The main loop is 9.5 miles -- a well maintained crushed limestone trail with some hills. (In particular on the south side is about a mile long hill.) There are few road crossings, none with much traffic. Bikers and horses also use the trails. Most is wooded, but there are also some meadows and ponds. There are two hand pumps for water at parking lots along the main loop.