This fiesta could not exist without the toro bravo, a species of bull from an ancient breed that only exists in Spain. This bull's forebears, the primitive urus, were spread out over wide areas of the world. Many civilizations revered them; the bull cults on the Greek island of Crete are very well known. The Bible tells of sacrificing bulls to honor divine justice.
Bulls also played an important role in the religious ceremonies of the Iberian tribes living in Spain in prehistoric times. The origins of the plaza de toros (bullring) are probably not the Roman amphitheaters but rather the Celtic-Iberian temples where those ceremonies were held. Near Numancia in the province of Soria one of them has survived, and it is thought that bulls were sacrificed to the gods there.
While religious bull cults date back to the Iberians, it was the Greek and Roman influences that converted it into a spectacle. During the Middle Ages the aristocracy, for entertainment, would torear (bullfight) on horseback — a style known as suerte de cañas. In the 18th century, this tradition was more or less abandoned and the poorer population invented bullfighting on foot. Francisco Romero was a key figure in laying down the rules for the new sport. If you are not familiar with corridas de toros (bullfights), here is what happens, so that you can decide for yourself whether you want to see one when you are in Spain. A corrida starts with the paseillo, when everybody involved in the bullfight enters the ring and presents themselves to the president and public.
Two alguacilillos on horseback look up to the president's box and symbolically ask for the keys to the puerta de los toriles. Behind that door, the bulls are waiting. When the door opens and the first bull enters, the real spectacle begins. It consists of three parts, called tercios (thirds), each announced with a bugle call. There are three toreros (bullfighters) — the better-known word "toreador" is actually never used in modern Spanish — in a corrida, each being allotted two bulls.
In the first tercio the torero uses the capote, a rather large cape that is a pinkish-mauve color on one side and yellow on the other. Now the two picadores enter on horseback, armed with a sort of lance. The second tercio is la suerte de banderillas. Three banderilleros must stick a pair of banderillas into charging bull's base of the neck. In the final suerte suprema, the bullfighter uses the muleta, a small red cloth draped from a stick. He must show his mastery to dominate the bull and establish an artistic symbiosis between man and beast. The corrida ends with the torero using his sword to kill the bull.