Spotted today on BLDGBLOG's Instagram page is a faux-brownstone in Brooklyn Heights that houses a secret subway exit. The Potemkinesque structure blends in nearly seamlessly with its brick-clad Neo-Georgian neighbors on 58 Joralemon Street, save for its blacked-out windows that mask the emergency stairway and ventilation shafts within. Peering through the keyhole, however, reveals the house's secret. The emergency exit is just one of many ascending from the train lines passing under the East River to Brooklyn and Brooklyn, says the Brooklyn Eagle. Here, many lines meet before spreading out over the burrough, a spatially confined condition which necessitates numerous points of egress in the event of an emergency. Although the house's true function isn't well known outside the neighborhood, the MTA has increased security of the decoy structure for fear that terrorists would force their way in and have access to subway tunnels and ventilation systems. File this under all of the city's (and BLDGBLOG's other well-documented) gutterspaces!