The traditional celebration takes place in San Bartolome de Pinares every January 16, the eve of Saint Anthony's Day, Spain's patron saint of animals.
Each year, residents light bonfires, before horses and their riders leap from the cobble-stoned streets through the flames in a spectacle described by one onlooker as "amazing".
According to tradition, the horses are 'purified' by the smoke and flames of the bonfires for the coming year.
As part of the preparation, the horses' manes are braided to protect them from being burnt.
The event has been criticized by animal rights groups over the years.
One visitor to the festival told Reuters that the horses were not harmed, claiming that "they jump by themselves and nothing happens to them".