“Cy Twombly: Treatise on the Veil” ostentatiously combines two museum trends: exhibitions built around one important painting, and the growing urge of museums of all kinds to feature modern and contemporary art. Here the yen for newness is lavishly advertised by a show centering on the billboard-size painting “Treatise on the Veil (Second Version),” a panoramic canvas measuring nearly 33 feet across that Cy Twombly (1928-2011) made in Rome in 1970.

The painting, from the Menil Collection in Houston, is displayed in what seems like splendid isolation despite the presence of 10 large related collages, some of which incorporate cardboard and plywood.