From the Super Mario Wiki
The Ventas Bullring (properly Plaza de Toros de Las Ventas) is a bullring in Madrid. Alongside the Palacio de las Cortes and the Prado Museum, it is one of the landmarks in Madrid in Mario is Missing!, although it is exclusive to the DOS and Deluxe versions. It gets raided by Koopa Troopas who steal a Matador's Cape; this causes the entire arena to shut down. Said cape is later retrieved by Luigi as he explores the city. He then brings it to the Ventas Bullring's information booth, at which point he is required to prove that the article of clothing is genuine (which he does by answering some questions, seen below). After this process, the arena is reopened to the public.
The corrida, Spanish for bullfight, competes with soccer for the favorite sport of Spain. Pitting man against beast, the bullfight has strict rules and customs. Like a play, the fight is completed in three main acts. Played before a judge, a good bullfighter, or matador, shows his bravery by letting the bull pass as close to his body as possible. The battle ends with the death of the bull, although many matadors have died. Manolete, one matador killed in the ring, is still considered the best of all time.