The Coignet Stone Company Building in Gowanus, Brooklyn.
Built in 1872-73, this is the last remaining structure of the Coignet Stone Company complex, which occupied five acres of land along the Gowanus Canal. The company manufactured a type of pre-cast cement material patented by Frenchman François Coignet. This material was used in St. Patrick's Cathedral, the Metropolitan Museum, and the American Museum of Natural History, as well as an alternative to brownstone in residential buildings. The company boasted that it could produce the facade of a building in a single day. This building looks like a mansion, but it actually served as a showcase for the product, and is the oldest remaining concrete structure of its type in New York.
The Coignet Company went out of business in 1882. The building was used by the Brooklyn Improvement Company until 1957. In the mid-1960s, it was covered in imitation red brick and had various occupants, but by the 1980s it was abandoned and left to deteriorate. Nonetheless, in 2006 it was designated a New York City Landmark.
The previous year, Whole Foods had bought the Coignet factory site, though not including this building. Whole Foods agreed to pay for its restoration, I guess as part of a deal to secure permits and zoning for the rest of the property, or maybe just because they didn't want a dilapidated eyesore next to their fancy new supermarket. Whole Foods built their store, and after a few lawsuits and fines were levied, made good on their promise to fund the building's restoration, even being awarded the Lucy G. Moses Preservation Award for "excellence in restoration" by the New York Landmarks Conservancy.
The building was then put on the market for $5 million, and then again in 2019 for $6.5 million. However, there were no buyers, because despite the excellence in restoration to the exterior, the interior is still dilapidated. It's currently back on the market with an asking price of $2.99 million.