The photo below is the start for this paved trail at Devon and Caldwell Avenues in northwest Chicago, just west of Central. It then runs about 20 miles north to Cook County Forest Preserve's Chicago Botanic Gardens. At the north end, a four mile loop runs around the Skokie Lagoons, and at the far northern end of the loop you can cross Dundee Road and enter the Chicago Botanic Gardens through an open gate, after which you bike the service drive to the entrance area. Entrance for pedestrians and bikers is free, and the Gardens provides bike racks.
TIP: Walking through their magnificent gardens is free and worth an hour or more exploration. I especially like the Japanese Island and the Rose Garden. A cafeteria is also available there. Then, if you exit the Botanic Gardens parking lot on the north and bike east on Lake-Cook Road about a mile, you can connect with the 10 mile Green Bay Trail. There is a sidewalk you can use on the north side of Lake-Cook Road if traffic is heavy, and the Green Bay Trail is just over the railroad tracks, heading both north and south from Lake-Cook Road.
Most of the trail passes through lovely forest, though the trail also passes two prairie restorations in Miami Woods and Bunker Hill Woods. You'll also pass a number of golf courses, two equestrian centers, meadows, numerous picnic areas, Jensen toboggan slides, and only occasionally are there views of residences or a commercial area. I took these shots after three days of winds as high as 55 MPH, explaining the debris on the trail, but only one downed tree was blocking the trail for its entire length.
Overpasses take you over the busy Lake Avenue (seen here) and the dangerous intersection of Oakton and Caldwell, and an underpass takes you beneath the Edens Expressway (I-94). Most other main roads the trail intersects have traffic signals. A bridle path parallels the bike trail for much of its length but is seldom seen, and a narrow gravel jogging/walking path abuts a section of the trail. The bridle path uses this same bridge, but the equestrians are on the other side of the farthest (curved) concrete wall.
The trail often runs near the river, but not usually this close! Several weeks of rain have the river well above flood stage, but the trail is constructed high enough so that no water encroached anywhere on the bike trail, although I did see the bridle path flooded in several places. Also, the dams and boat launch at Skokie Lagoons were completely under water.
Lest you think I oversell the glories of visiting the Chicago Botanic Garden, look at these incentives:
Below are the maps of the north and south sections of the trail: