The Old Post Office

This guide to The Old Post Office in Chicago starts in 1921, when architects raised nine stories of limestone by the river and punched a two-story hole through its base for a highway that existed only as a line on a map. It follows what that empty tunnel waited for over the following decades, and how the building above it grew into the largest post office on earth, moving mail for two rival catalog giants. The post office moved out in 1997, and a British developer later spent seven years trying and failing to redevelop the place. Look up at the arch as you pass beneath it.