It's a gorgeous 6.9 mile, very hilly, one-way trail…unless you make it an out-and-back. If so, plan on about 14 lovely miles round-trip.
While you can begin at any of the four different PPD parks, if you start from the north side at Camp Wokanda you can expect parking, reserved camping and restroom facilities near the trailhead. Following the IRBT signs, you'll hike up about two miles into Robinson Park, where there is additional parking and restroom facilities. From Robinson Park, continue the up-and-down hilly hike towards Green Valley Camp, at mile 5.5, which is an old Salvation Army summer camp (no longer in use). On the way there, you'll pass under IL Route 6 via a tunnel for walkers.
Once you reach the Green Valley Camp, you are almost to Detweiller Park…but wait! The journey still has some large ascents and descents in store for you for the last 1.4 miles. Once you've reached Detweiller Road in the park, there's a short detour across the road to pick up the last section of the trail, which ends in the main parking lot of Detweiller Park. Be sure to keep an eye out for cool bridges and tunnels at many turns.