Petit Chateau was a Châteauesque mansion at 660 Fifth Avenue on the Upper East Side in New York City. It was built for William Kissam Vanderbilt & Alva Vanderbilt from 1878 to 1882. Determined to make her mark in New York society, Alva Vanderbilt worked with the architect, Richard Morris Hunt, to create the French Renaissance-style chateau. It was sold to a real-estate developer in 1926 & demolished. In a draft of her memoirs, Alva, then Mrs. Belmont, merely noted the demolition in passing.