What is a sumo arena called?

Sumo matches take place in a dohyō (土俵): a ring, 4.55 metres in diameter and 16.26 square meters in area, of rice-straw bales on top of a platform made of clay mixed with sand. A new dohyō is built for each tournament by the yobidashi. At the center are two white lines, the shikiri-sen, behind which the wrestlers position themselves at the start of the bout.