Spain kicked off one of its most controversial and adrenaline-fueled traditions on Monday: the Pamplona bull run. As part of the nine-day San Fermín Festival held every year from July 6 to July 14, the event brings more than a million thrill-seekers and spectators from across the globe to the city of Pamplona to watch hundreds of brave revelers

Tens of thousands of revelers have packed Pamplona’s town hall square in northern Spain to celebrate the traditional firework blast that marks the start of the San Fermín bull-running festival.

Thousands of revelers ran, skidded and tumbled out of the way of a stampeding group of bulls at the opening run of the San Fermín festival in Spain on Monday. This is a photo gallery