The national sumo stadium hosts three grand tournaments a year — January, May, and September — each lasting 15 days. The ancient ritual is mesmerizing: salt flies into the air, two enormous wrestlers crouch, then slam together in a flurry of slapping and heaving that's over in seconds. Rent an English commentary radio, grab a bowl of chanko-nabe (the protein-rich stew eaten by wrestlers) in the basement cafeteria, and settle in for an afternoon of Japan's most viscerally thrilling traditional spectacle.