7 Wonders of Chicago

I generally mark a place done if I have gone inside of it and put my feet on the ground/floor no matter how long. 10 seconds will do the trick. Now, obviously, 10 seconds isn’t enough to really explore the Museum of Science and Industry. Or the Lakefront. But perhaps it is too long at Wrigley Field (I’m joking).

Anyway, I’d pick a standard and go with it.