World's Coolest Observation Decks

The Willis (formerly Sears) Tower, Chicago

How do you make the observation deck of a 37-year-old skyscraper that hasn’t been the world’s tallest since 1998 feel new again? You attach a series of magnificently scary glass boxes, collectively known as the Ledge, to the venerable Skydeck. The illusion that you’re standing unsupported 103 stories above the ground is a real crowd-pleaser.

Observe This: The boxes are hung from a moving steel frame that allows them to be retracted into the building to make way for the window-washing rig. —Karrie Jacobs