One of the finest and most intact of the lavish estates built by wealthy 19th-century industrialists along the Hudson, Frederick William Vanderbilt's 54-room country palace in Hyde Park, built in 1898, is a no-holds-barred gem. One of the first steel-framed houses in the U.S., at 55,000 square feet (on 670 acres), it was the smallest and least expensive of the famed Vanderbilt mansions (others were in Newport, Bar Harbor, and Asheville), but it still epitomized the Gilded Age's nouveau riche. French in every respect, from Louise's Versailles-like bedroom to the grand dining room and Frederick's glittering master bedroom, it was decorated in impressively grand style. Yet the house, where the Vanderbilts spent only a few weeks each year in the spring and fall, functioned as a kind of spa retreat. Guests were encouraged to enjoy the outdoors: the majestic views of the Hudson and Catskills in the distance and the wonderful gardens and woodlands surrounding the house.