The Loop - Chicago is a 3.5 mile loop trail located near Chicago, IL and is good for all skill levels. The trail is primarily used for hiking and walking and is accessible year-round.
A nice walk in downtown, people, buildings
Best way to see Downtown Chicago is by walking through it. Recently I visited the Field Museum and I wanted to explore Downtown Chicago. So I followed the Columbus and walked toward Downtown, around the Millenium Park, I turned to the River Walk, and then back to the Michigan Ave. Finally I arrived at the Lincoln Park. The walk was nice and it allowed me to see the Chicago at the street level.
Nice little walk through Chicago, can't really call it a trail though.
You can ramble about the Loop downtown area, but the best walk is one led by a docent from the Chicago Architectural Foundation. They even lead tours from river boats. The city itself is a museum of various excellent styles of styles.