The tiny country of Luxembourg opened its spectacular new I.M. Pei-designed modern art museum this month, an enterprise nearly twenty years in the making. “Still, this striking symbol of modernity is not quite what its name implies. Because Luxembourg owned virtually no Modern art, and the museum could hardly afford to start building a collection of works by, say, Picasso, Braque, Matisse, Dalí, Miró and the like, this is really a museum of contemporary art… The size and sober grandeur of Mr. Pei’s building still suggests a museum awaiting a collection. But at least the museum exists, something that at times seemed less than certain.”