Unlike a boxing ring, a sumo ring is actually round. In this Edo-era print, you see a high-ranking yokozuna (grand champion) entering a ring wearing a ceremonial apron, with white streamers patterned after the white streamers in front of Shinto shrines. The yokozuna is followed by two other rikishi (high-ranked wrestlers) who serve as escorts during ceremonies. The dohyo (ring) is roughly half a meter high (18 inches), and the edge is marked by straw bales buried in the ring.
One a match begins, the apron is discarded, leaving just two rikishi, clad only in mawashi (silk loin cloths). Matches tend to be short, since there are virtually no rules: you win if you force your opponent out of the ring, or force any part of the opponent's body (other than the soles of the feet) to touch the ground. The ring is a little more than five meters across (17 feet), leaving very little margin for maneuver or error.