Stickney Sewage Works, Illinois

The Stickney Water Reclamation Plant is one of the largest sewage treatment plants in the world. It serves a 260-square mile area, with around 2.3 million people. Up to 1,440 million gallons of sewage per day can be treated in the 166 tanks at this 413-acre site, which has its own railway with 30 miles of track.