You can all thank my buddy Riley Tsang for putting a rusty old shopping cart on top of a few carefully-stacked planks of wood. These strange objects denote your entrance to this cozy yet intriguing little abandoned building. I call it a shack because it only includes about four rooms total, but with two levels and plenty of places to climb, it's definitely one I'll go back to (especially because it's close to so many other sites on this list).
Park at Doyne Park on 5300 W Wells Street. If you're looking for the building, the coordinates are 43°02’28.3”N and 87°58’09.2”W. Climb up the planks of wood (and shopping cart pieces) to reach the second floor of the little shack. Don't worry - it's sturdier than you think. No one's died yet.
Have you been to this site? What did you think? Leave any tips of your own or observations in the comments to help other explorers!