In a gutsy move for both artist and institution, Robert Grosvenor’s first museum exhibition in more than a decade consisted of a single work—and one created almost thirty years ago. Entering the exhibition space through a small vestibule, one immediately came face-to-face with Untitled, 1989–90, an enigmatic construction sitting, sphinxlike, in the Renaissance Society’s dramatically vaulted gallery. Two parallel walls of silver-painted cinder blocks, each six units high, were positioned directly on the gallery’s mottled gray linoleum floor. Extending from the leftward end of each wall was