The San Antolin festival, held every year between the 1st and 8th September, reaches its peak on September 5th with the "Antzar Eguna" or the day of the geese, one of the most popular festivals in the province. It is a spectacular and original tradition with deep roots in ancient rituals, with documented evidence dating back more than 350 years.

Saint Antolin's Day in Lekeitio (Biscay) marks the day on which festival-goers "run the goose", by way of an age-old fiesta once celebrated the length and breadth of the Basque Country. The game consists of decapitating a dead goose hanging from a rope in the middle of the harbour - with nothing but their body weight and the strength in their arms.

Coming alongside the hanging goose, the participant grabs the neck of the animal and jumps into the water. Meanwhile, a group of "sailors" - usually youngsters from the town - pull on the end of the rope, sending both goose and player into the air. The sailors then release the rope, sending both plunging back into the water. The idea is to try and separate the animal's body from its head while withstanding this vigorous jostling.

Traditionally, the "Antzar Eguna" has formed part of the San Antolín festival since 1877, though at various times throughout the past it has formed part of other celebrations, such as the Andra Mari festival of August, or in San Roque. It used to be performed in the village square, but since 1722 the event has taken place in water.

It is also known that since 1622 only sailors were allowed to participate and that the boats used to approach the goose had to have 12 rowers plus the skipper. If there was any doubt as to the winner, the solution would be to hold a boat race, completing one lap round the Island of San Nicolás, which is located opposite Lekeitio Bay.