The Windy City / Chi Town in Illinois is the third most populous city in the United States. If you have never been to Chicago you should start at the Loop, the city center and business district of Chicago. From there on you can walk the Magnificent Mile, where all the amazing boutiques, restaurants and hotels are located. It is a small version of 5th Avenue in NYC.
When the windy city is not too cold and too windy you could take a walk around Navy Pier, which is just east of downtown directly next to Lake Michigan. There you can find a lot of dining, water taxi and dinner cruises options. Not far away at Millennium Park you can take a look at the Cloud Gate / The Bean. It is a sculpture by artist Anish Kapoor. The Bean reflects the city’s skyline. A lot of tourists go there to take funny pictures.
Teddy’s hint: Regarding the food culture Chicago is known for its Chicago-style pizza called deep-dish pizza. You have to go to Pizzeria Uno where the thin crust pizza style originated. You won’t get bored in Chicago. There are countless nightlife possibilities such as theatres, to Soul, Blues or Jazz concerts or just enjoy one of the outdoor summer festivals.