Despite its Spanish Colonial belfries and arches, the McNay Art Museum’s strong suit is Impressionist and modern art (Van Gogh, Picasso, O’Keeffe, Pollock). Fittingly, Parisian architect Jean-Paul Viguier’s spare expansion of the San Antonio museum puts a modern twist on the original 1920’s buildings with a sleek, 45,000-square-foot glass box (6000 N. New Braunfels, 210/824-5368; The newly christened Jane and Arthur Stieren Center for Exhibitions nearly doubles the institution’s overall space. Transparency defines the new structure: adjustable louvers atop the skylit roof and retractable silkscreened glass beneath it modulate the daylight with such refinement that the shadow of a passing cloud is perceptible. Gardens extend from the glass-walled galleries down to the McNay’s lush grounds and outdoor sculptures, including large works by Barbara Hepworth and Anthony Caro. On view now through January 4: “Judith Godwin: Early Abstractions,” an exhibit devoted to the American Expressionist painter. Opening on October 22, “Artmatters 13: Joseph Marioni: Liquid Light.”