Chicago, Illinois is home to some of the country's most iconic skyscrapers, but with downtown real estate at a premium and with commuting times among the nation's worst, some have proposed a new solution: an Underground City. By building 1,000 feet directly beneath the Loop, the city could solve its space crunch and provide homes, offices, and more to tens of thousands of people. Drawing on lessons learned in Moscow - home to the world's deepest subway system - and Amsterdam - where planners hope to build beneath the city's canals, an underground city beneath Chicago is not only technologically possible, but might one day be necessary.