11 Forgotten Underground Tunnels in the U.S. That Time Left Behind

The Dupont Underground, Washington D.C

The Dupont Underground in Washington D.C. is a series of tunnels that were originally built as a streetcar system in the 1940s. After the streetcars ceased operation, the tunnels were used for various purposes, including as a fallout shelter during the Cold War. Today, they are a popular location for urban explorers and artists.