A real find among the city's museums, this collection housed in an exquisite Beaux Arts mansion on the Upper East Side represents the personal holdings of Henry Clay Frick. The 19th-century industrialist had excellent taste: Among the exhibits are rare collections of Limoges enamels, Chinese porcelains, French 18th-century furniture, and a who's who of painters from Rembrandt to Gainsborough to Vermeer