***SPONSOR SALE*** Imagine a once-in-a-lifetime, blank-slate opportunity to craft an unrivaled penthouse residence just off Fifth Avenue and across the street from the Guggenheim. This ESTATE CONDITION Carnegie Hill three-bedroom, three-and-a-half-bath, Gilded Age duplex delivers all that and more with regal pre-war details including a wood-burning fireplace, large private terrace and modern condo...