The Lowline (http://www.thelowline.org) proposes to use solar technology to illuminate an historic trolley terminal on the Lower East Side of New York City, in order to create an underground park.  The site was opened in 1908 for trolley car passengers, but has been unused since 1948 when the service was discontinued. Despite such a long period of neglect, the space is said to still retain beautiful original features such as cobblestones and vaulted ceilings. It is also adjacent to an existing subway station to encourage people from all across the city to visit and enjoy the park, even in winter.  Although funding and planning approval are yet to be finalised, the project appears to have strong public backing in principle. If opened in 2017 as scheduled, the Lowline could act as a game changer in people’s perceptions of underground public spaces.