There are Brooklyn townhouses, and then there's the 17,500-square-foot mansion on Pierrepont Place. Located right along the Brooklyn Heights promenade, it just hit the market asking a hair-raising $40 million. The WSJ first reported Corcoran townhouse guru Vicki Negron's blockbuster listing. Called the Low Mansion, it was completed in 1857. The original owner, A. A. Low, was a businessman, and his son Seth was the mayor of Brooklyn before the five-borough system was adopted in 1898, and became mayor of the whole city in 1902. The younger Low was also president of Columbia, and the powerful father-son duo truly defined early Brooklyn Heights history (as well as real estate). When it lists, the home will oust the current record-holder for most expensive Brooklyn property: a $32 million penthouse, not far away at One Brooklyn Bridge Park. Consider the priciest parcels of Brooklyn real estatethis blows them out of the water.