08/07/2026
666 PARK AVE - NYC'S MOST PALATIAL AND MYSTERIOUS MAISONETTE! Custom designed for a Vanderbilt who never moved in, the triplex maisonette at 660 Park Avenue—which debuted with a custom address of 666 Park—is hidden within the base of one of the most exclusive co-ops on the Upper East Side. See inside the 27-room relic of prewar NYC, here: https://robertkhederian.substack.com/p/666-park-ave-maisonette-history-photos