From the world’s largest rooftop farm to stunning private gardens, we’ve seen a lot of amazing designs on New York City rooftops, but who would have thought to place an entire house atop a Big Apple building? More people than you would think, that’s for sure. The idea of a rooftop house may seem extravagant, but open space is sparse in the concrete jungle, and often there’s no place to go but up. Hit the jump to see eight amazing hidden houses that create no additional footprint and offer a unique twist on green roofs.