Runners are chased by a pack of fighting bulls during a bull run through the streets of Pamplona, northern Spain, on Saturday. Spain's most famous fiesta, the San Fermin bull-running festival, was popularized internationally by Ernest Hemingway's 1926 novel "The Sun Also Rises." The Sanfermines, held since 1591, attracts tens of thousands of foreign visitors each year for nine days of revelry, morning bull runs and afternoon bullfights.