South of Chicago, maybe 30 minutes. 9.2 mile crushed limestone loop through the forest around Argonne National Laboratory. Some light up/down. Very solid overall if you're looking to get out of the city. Runners, hikers, and bikers all use the trail; it is quite wide so no crowding issue. Take 55 south to Cass Ave (south I thing, 273A or 274A, there's a sign for Argonne). From Cass you'll take a right at Argonne sign within first half mile...can't miss it.