THREE LARGE DISKS (two white, one black), each padded and covered with silk, protruded from the walls of one room. In the next, a small marble tablet advised that behind the wall (which had been sealed off with painted white bricks) a man was diving. The third and final space held three large tablets, again in marble, one bearing a cell-phone number, the others the message (in Italian and English) that the telephone company transmits to advise callers that a recipient's service has been turned off. In his most recent show, the thirty-seven-year-old Venetian Giovanni Rizzoli presented himself in