The Plaza México, situated in Mexico City, is the world's largest bullring. This 41,262-seat facility is usually dedicated to bullfighting, but many boxing fights have been held there as well, including Julio César Chávez's third bout with Frankie Randall  The Plaza México replaced the ancient bullbag Toreo de la Condesa in the Condesa neighborhood that was overwhelmed by the rapid development of the Mexican population. It opened on 5 February 1946 and annually since then, that date marks the date of the Corrida de Aniversario.

http://en.wikipedia.org/wiki/Plaza_M%C3%A9xico