7. The Second Mrs. Astor’s House, 840 Fifth Avenue
Caroline Astor moved to this spot on Fifth Avenue after her nephew, William Astor, built the original Waldorf Hotel next door to her home. She traveled up to 65th Street and Fifth Avenue and hired Richard Morris Hunt to build a mansion for her and her son John Jacob Astor. The two residences were connected by a ballroom that could hold 1,200 guests (the same amount of guests that Alva Vanderbilt had invited to her fancy dress ball). John Jacob Astor renovated his mother’s side of the mansion after she died, but he himself wouldn’t live long enough to enjoy it. Astor was one of the many casualties of the doomed RMS Titanic. As per Astor’s will, his new wife was forced to give up the mansion, which went to Astor’s son from his first marriage, William Vincent Astor. Preferring his estate out on Long Island, William sold the 65th Street property to developers and auctioned off the interiors. Today the Temple Emanu-El stands in its place.