New York City’s Riverside Park spans a number of neighborhoods including Harlem, Morningside Heights and the Upper West Side. Here are the top 10 secrets you might not have known about Riverside Park in New York City, including a murder involving a member of the Beat Generation and the park’s bird sanctuary.

10. There’s a “Freedom Tunnel” Under Riverside Park

Just under the surface of Riverside Park is a three mile long train tunnel commonly known as the Freedom Tunnel. The tunnel was designed by Robert Moses in the 1930s to provide more park space above for neighborhood residents. It was used for freight trains from the time it was built until the 1980s, when it was subsequently closed. Following the tunnel’s closure, the homeless sought refuge from the streets inside the vast tunnel, with hundreds of people living underground at its peak in the ’80s and ’90s. Amtrak reopened the tunnel in 1991, and trains still run through there today. Although we don’t recommend any kind of trespassing, do be careful if you go in there.

The tunnel gets its name from its best known graffiti artist, Chris “Freedom” Pape. As Untapped Cities previously reported, Amtrak began painting over much of the art in 2009, including a number of works by Pape. See more photos here.