3. There is a Network of Underground Tunnels Under Columbia

Tunnels beneath Columbia University

What is now possibly the worst kept secret is the intricate network of tunnels that connects many of the school’s buildings. The tunnels date back to the days of the Bloomingdale’s Insane Asylum. The tunnels are still in use today, though the university is increasingly limiting access due to rogue tunnel explorers and other hazards, many of which are remains from another famous use for the tunnels: the Manhattan Project.