After Prospect Park opened in 1867, a wave of development hit the surrounding area, now known as Park Slope. The stretch of Prospect Park West, which bordered the park, was dubbed the “Gold Coast” for its many lavish mansions. Today, the stretch is still home to some of Brooklyn’s most impressive buildings. This townhouse at 103 Prospect Park West is one of them. A triplex co-op there is on the market for $1.995 million, and it retains much of its pre-war detailing.