is the ring in which sumo
bouts are fought. Placed on top of the dohyo
(a large platform built out of clay), the shobudawara is marked out by almost-buried bales of rice straw
("sho-bu" is "win-lose" and "dawara" (tawara
) is the bale of straw). A sumo wrestler who touches the ground outside the shobudawara after the match has begun - if only with a toe - has lost1
The shobudawara is 455cm in diameter. The edge is made up of 20 tawara, 4 of which (east, south, west, and north) are pulled slightly back. These are the 4 "points of virtue" - the tokudawara. Originally this was where the sumotori (sumo wrestlers) and gyoji (referees) entered and left the ring. Also, these pulled-back tawara allowed for rainwater to drain off in times when sumo was fought outside.
As the shobudawara is not level with the dohyo floor, the wrestlers can get foothold on the tawara, and maybe stop themselves from being pushed out of the ring. Some wrestlers actually teach themselves to run along the shobudawara, not touching the floor on either side.
- Once a bout has begun a sumotori loses if he touches the ground within the shobudawara with anything but the soles of his feet or if he touches the ground outside.
My sources are mainly http://www.sumo.or.jp/eng and Sumoforum's wonderful glossary.