When you think of NYC parks, the first that come to mind are probably the famous Central Park and Prospect Park. However, sometimes it’s the local and lesser-known parks that have the best secrets. McCarren Park in Brooklyn is one great example. McCarren Park is a 35-acre hub of constant activity and diverse frequenters, bordered by Nassau Avenue, Bayard Street, Lorimer Street, and North 12th street. First conceived in 1903, it’s now home to a track, a variety of athletic fields and courts, and an outdoor Olympic-sized pool that reopened in 2012. From hidden tunnels to artwork, here are the top ten secrets of McCarren Park.

1. The McCarren Park Pool Has a Network of Secret Tunnels

The McCarren Park Pool—a designated historic landmark— was built in 1936 by Robert Moses as one of eleven public pools with Works Progress Administration funding. These massive pools were built with enormous filtration and heating systems, along with underwater lighting. To support this behind-the-scenes infrastructure, McCarren Pool features a rarely seen tunnel network that rings the entire perimeter of the pool, connecting a former boiler room under the entrance arches to the filtration plant in the rear. There are more photos of these tunnels along with a complete retrospective of McCarren Pool’s “dark” days of abandonment here. The pool fell into disrepair and eventually closed in 1984. After restoration, it reopened in 2012.