ABC News October 8, 2018

Stunning pictures show Catalonia's 'human towers,' a biannual historic tradition

WATCH: Stunning video shows 'human towers' of Catalonia

Images of one of Catalonia’s oldest traditions – the biannual ‘human tower’ competition in Tarragona, Spain -- have been captured in stunning photos.

Emilio Morenatti/AP
Members of "Castellers de Sants" complete their human tower during the 27th Human Tower Competition in Tarragona, Spain, Oct. 7, 2018. The tradition of building human towers or "castells" dates back to the 18th century and takes place during festivals in Catalonia, where "colles" or teams compete to build the tallest and most complicated towers. "Castells" were declared by UNESCO one of the Masterpieces of the Oral and Intangible Heritage of Humanity.

The competition is not usually political, but proceedings began on Sunday with a five-minute protest from Catalan separatists who want independence from the rest of Spain, according to Reuters. Over 6,000 spectators attended the event in northeastern Spain.

(MORE: 'This fire is still alive': A year after Spain extinguished Catalonia’s secession attempt)
Maja Hitij/Getty Images
Members of the C. de Barcellona built a human tower during the 27th Tarragona Competition, Oct. 7, 2018, in Tarragona, Spain. The 'Castellers' who build the human towers with precise techniques compete in groups, know as 'colles', at local festivals with aim to build the highest and most complex human tower. The Catalan tradition is believed to have originated from human towers built at the end of the 18th century by dance groups and is part of the Catalan culture.

One year on from when a controversial independence referendum was held on Oct. 1 2017, the region is still deeply divided. Many see Catalonia as completely separate from Spain, often pointing to its different linguistic and cultural traditions as proof.

The human towers, or ‘castells’, were inscribed in 2010 on UNESCO’s list of the intangible cultural heritage of humanity.

Forming the towers requires ‘castellers’ to stand on one another's shoulders, stretching higher and higher. Anyone is welcome to join in and support the foundation of the incredible structure, which is why such large crowds gather at the base.

Sandra Montanez/Getty Images
Members of Castellers de Sants fall down as they built a human tower during the 27th Tarragona Competition, Oct. 07, 2018, in Tarragona, Spain. The 'Castellers' who build the human towers with precise techniques compete in groups, know as 'colles', at local festivals with aim to build the highest and most complex human tower. The Catalan tradition is believed to have originated from human towers built at the end of the 18th century by dance groups and is part of the Catalan culture.
(MORE: Catalan president claims mandate for independence but seeks dialogue with Spain first)

Each level of the tower is known as a tronc, and the highest levels of the tower usually comprise young children.

Sandra Montanez/Getty Images
Members of Colla Vella dels Xiquets de Valls build a human tower during the 27th Tarragona Competition, Oct. 07, 2018 in Tarragona, Spain.

The tradition dates back to the 18th century, according to the AP.

Albert Gea/Reuters
Members of group "Colla Joves Xiquets de Valls" form a human tower called "castell" during a biannual human tower competition in Tarragona, Spain, Oct.r 7, 2018.

A number of Catalan separatist leaders were jailed last year, and the Spanish Supreme Court is set to consider their cases in November, according to Politico.