Ryōgoku Kokugikan, Tokyo's major sumo arena, is now on Street View. You can walk around the arena and look down on the sumo ring from the top of the 13,000 capacity stadium. You can even wander down and stand in the ring itself.
However there are 68 sumo wrestlers guarding the arena and to gain entrance you do have to fight and beat them all. Warning - this is what happened to me when I tried: