Sears Tower's Ledge lets tourists step onto glass floors 1,353 feet above Chicago's sidewalks. Each box weighs 1,500 pounds, built from three layers of half-inch glass. It's engineered to hold 10,000 pounds. No one leans out a window to clean it. A motor pulls the whole box back on rails, straight into the building, then slides back out over the drop. The boxes are still open every day, right now.
