From an 1890s carriage house to this stunning modern home, the Park Slope property at 77 Prospect Place has quite the story behind it. According to Brownstoner, this building, along with two others, was purchased by the Brooklyn Union Gas company for use in an alternative energy experiment. 77 Prospect served as the company’s show house, and they installed experimental fuel cells on the roofs, the design of which was inspired by the Apollo spacecraft. More recently, in 2004, the building was completely renovated by the architect Philippe Baumann. He built out a chic, modern interior and added a second floor with a stunning open space that opens to an outdoor patio with a hot tub. Now it’s up for grabs, asking $7.495 million.