The American Wing of the Metropolitan Museum of Art has an airy, skylit atrium, the recently remodeled Engelhard Sculpture Court, a place overflowing with marble and curious marvels. In one corner, the Vanderbilts’ humongous hearth. Over there, glowing Tiffany windows. Catty-corner is an annexed Frank Lloyd Wright living room, transplanted entire from Minnesota. But the main draw, anyone can see, is the café. . . .