Oh my goodness.
At first I thought Chicago was going to be all Frank Lloyd Wright (who I blame for messing up a perfectly lovely waterfall that was minding its own business) and weird sculptures and didn't think there would be anything I'd be interested in.
Now it's the opposite problem--so much I want to see and so little time!
When I google map how to get from here to there walking, it keeps telling me to take the Pedway, which I gather is a bunch of pedestrian tunnels and stairs. Can you still walk along the sidewalks everywhere to get around, or do you have to walk through tunnels and up stairs on certain routes?
If you're looking for Frank Lloyd Wright, you'll find little of him in the downtown area. The most famous example of Wright's work downtown is The Rookery Building light court, and even that does not reflect his Prairie School style.
img src - therookerybuilding.com
If Wright interests you, taking the CTA Green Line or Metra-Union Pacific West to Oak Park would be your best bet, where a number of homes and the Unity Temple (which just received an extensive restoration) reside.
Within Chicago city limits, The Robie House is one of the better known Wright works. It's located within the confines of the University of Chicago Campus. I do not know what the tour policies are; though it is on the list of "Open House Chicago", it will only be available on Sunday.
The whole area is worthy of a day, really. The Oriental Institute, which is an incredible, but often overlooked, museum is right there. The Rockefeller Chapel, also nearby, sits along the Midway Plaisance. The Plaisance served as a carnival/sideshow midway during the Columbian Exposition of 1893. The U of Chicago campus sits on either side of the Plaisance, and links two massive city parks, Washington Park to the west and Jackson Park to the east.
On the west end of the Plaisance, sits Lorado Taft's sculpture, "The Fountain of Time".
img src - miarchitects.com
Another of Taft's works, "Fountain of the Great Lakes" can be found outside The Art Institute, a short walk from your hotel.
Washington Park contains the DuSable Museum of African-American History. I must confess that Washington Park is located in a somewhat rough patch of town at the moment, so if you consider visiting the park, best do so during the day.
On the east end of the Plaisance is Jackson Park, which was the location of the famed "White City" of the Columbian Exhibition. Jackson Park will be the future home of the Obama Presidential Library.
Within the park sits the Garden of the Phoenix, located on the north end of Wooded Island. The island sits in between Jackson Park's east and west lagoons. A pavilion built by Japan for the Columbian Exhibition once stood on the site of the garden. The pavilion was destroyed by fire shortly after WWII.
img src - gardenofthephoenix.org
Just south of Wooded Island stands The Statue of the Republic, a 1/3 scale reproduction of a statue that stood in the "White City"
img src - flickr.com
The north end of Jackson Park is the location of The Museum of Science and Industry, which one easily could spend a day or two exploring. The museum was originally the Palace of Fine Arts during the Columbian Exhibition, and the sole surviving structure from the "White City".
Among the museum's permanent collection are a captured WWII German U-Boat, a United Airlines Boeing 727, and, of interest to rail fans, the original Burlington Prairie Zephyr,
img src - chicagomusicguide.com
as well as an impressive model railroad display. The model display features a scale model of the portion of the Loop where you will be staying, by the way.
https://www.youtube.com/watch?v=ckBBmJhouzE
source - youtube.com
The whole area can be accessed by Metra Electric District trains, at both the 55th-56th-57th Street and the 59th Street stations. Pick up the Metra Electric at Millennium Station, which is a hop, skip, and a jump from your hotel.
Forgive the novel, but it's difficult to mention one destination without mentioning all the others nearby. Considering the limited amount of time you have, just save this for the next trip to Chicago.
ETA - video attribution