A polka dotted park? Yes, but beneath the land-art fun is an ingenious roof. Charged with extending the Städel Museum in Frankfurt am Main, Schneider + Schumacher decided to sink the new building below the museum’s garden, a gently-domed space illuminated by 195 roof lights. Dubbed “eyes for art,” the lights vary in diameter, from 1.5 meters at the outer edge to 2.5 at the center peak. Like eyelids, built-in shades mitigate daylight, winking at the 20th century contemporary art shown in this subterranean world.