Two words. Navy Pier.
It was built in 1916, marking 2016 as their 100th anniversary – so I’m sure there will be lots of special events to celebrate this year.
It’s about a 20 minute walk from the city center. They have small shops and food court type eateries (and were building more when I visited in September 2015). There was also a miniature arcade-type place so that was fun to check out. When I went, they were just taking down the ferris wheel. I assume they take this down each season since Chicago isn’t dubbed the Windy City for no reason. But I recently read on their site that it will be up and running again in no time. Navy Pier seems like it would be a great spot to hang out at during the summer since you can walk outside and get a great view of Chicago.