NEW YORK— Most New Yorkers have no idea that they may be walking above long-forgotten underground tunnels and railways, relics of the horse-drawn trolleys and electrified cars of the early 20th century. There are at least 13 acres of unused tunnels throughout the five boroughs, many of them unsafe and unusable. One such site is located underneath the Lower East Side (LES), and could soon become an unlikely green sanctuary. The Delancey Underground, site of the former Williamsburg Trolley Terminal, is a 1.5 acre area located at the LES foot entrance to the Williamsburg Bridge. This huge underground space — almost two-thirds the size of New York\'s Grammercy Park— is managed by New York\'s Metropolitan Transportation Authority (MTA). It was in active use from October 1905 until it was abandoned in 1948. Two men with a vision want to transform this deserted underground space into an incredible subterranean public park filled with light and greenery, utilizing cutting edge design and green technology. James Ramsey, a principal of the architectural firm RAAD Studio in New York and Dan Barasch, Vice President of the social innovation network PopTech, have charted the course from abandoned plot to public park. Delancey is one of the largest contiguous sites underground in all the boroughs, says Barasch. Not to mention, it\'s in an interesting part of the city. This area of Delancey Street is a vital corridor. Its history dates back to famed urban builder Robert Moses and the destruction of huge swaths of tenement buildings, homes to many first-generation immigrants fresh from Ellis Island, to make way for newer, more modern public housing.