Brownstones or brownstone houses refer to multi-storey single-family townhouses that were built before the 1900s using reddish brown sandstones. Before the turn of the century, they were built mostly by wealthy families and therefore, contain some of the most exquisite architectural details of the era. Today, these brownstones are highly desirable in New York City. The brownstones in this photo are from a cul-de-sac in Brooklyn Heights, a very prosperous neighborhood in New York City. Each of these unit can easily cost over $4 million.