These amazing photos of people constructing complex and terrifying human towers were taken at the 26th Concurs de Castells in Tarragona in the Catalonia region of Spain. The building matter used in the construction of each tower is people – up to 500 of them, working together in a tightly organised system.
Colla Vella dels Xiquets de Valls complete their human towerLluis Gene/AFP
Each tower is carefully planned and engineered, with members positioned according to weight and strength, so there are no weak links. The teams use different building techniques, resulting in complex patterns when viewed from above.
The strongest and heaviest members interlock their arms to form a stable base, and then most of the other team members form human buttresses radiating out from each tower, supporting and strengthening it. They also act as a safety net, cushioning the fall of people from the upper levels if the tower collapses.
Colla Jove Xiquets de Tarragona start to form a human towerAlbert Gea/ReutersCastellers de Vilafranca start to form a human towerAlbert Gea/ReutersColla Vella de Valls start to build a human towerDavid Ramos/Getty ImagesColla Vella dels Xiquets de Valls start to form a human towerLluis Gene/AFP
Then comes the hair-raising bit: constructing up to nine storeys, saving the lightest and youngest members for the upper levels. The most dangerous job of climbing to the pinnacle of the tower, saluting the crowd and then scrambling back down before the whole thing collapses is given to a girl as young as five. Accidents are rare, but there have been fatalities. In 2006 at a competition in Mataro, a 10-year-old girl fell to her death. The youngest members now wear foam-padded helmets.
Members of the Colla Vella dels Xiquets de Valls build the next level of their human towerLluis Gene/AFPYounger member of the Colla Joves Xiquets de Valls climb up to form the tower's upper levelsAlbert Gea/ReutersColla Vella dels Xiquets de Valls complete their human towerLluis Gene/AFPA supporter applauds as Colla Vella Xiquets de Valls complete a human towerAlbert Gea/ReutersColla Joves Xiquets de Valls fall down after forming a human towerAlbert Gea/ReutersMembers of the Colla Vella de Valls help a team mate who collapsedDavid Ramos/Getty ImagesMembers of the Colla Xiquets de Reus support the human towerDavid Ramos/Getty ImagesMembers of the Colla Xiquets de Hanghzou, who travelled all the way from China, support their team mates as they climb up to form the next level of a human towerDavid Ramos/Getty ImagesA member of Xiquets de Hanghzou takes pictures as the team builds a human towerDavid Ramos/Getty ImagesA young member of Castellers de Sant Cugat climbs up to form an upper level of the towerDavid Ramos/Getty ImagesColla Jove Xiquets de TarragonaAlbert Gea/ReutersMembers of various Colles watch their team members build a human towerDavid Ramos/Getty ImagesMembers of the Colla Sagals d'Osona react as a human tower is builtDavid Ramos/Getty Images
The teams compete over five rounds, with points awarded for height and complexity. This year's Concurs de Castells in Tarragona was contested by 32 teams from around Catalonia – and one from China. A tense final saw Vilafranca triumph for the eighth consecutive time.
Castellers de Vilafranca start to form a human towerAlbert Gea/ReutersAn aerial view of the arena as Castellers de Vilafranca form their human towerAlbert Gea/ReutersThe Colla Castellers de Vilafranca construct a human towerDavid Ramos/Getty ImagesCastellers de Vilafranca complete their human towerAlbert Gea/ReutersAs soon as Castellers de Vilafranca's tower is completed, it is allowed to collapseCastellers de Vilafranca celebrate after forming a human towerAlbert Gea/ReutersMembers of Castellers de Vilafranca celebrate after forming their human towerLluis Gene/AFPMembers of the Colla Castellers de Vilafranca celebrate after building a human towerDavid Ramos/Getty Images
Human towers are considered to be such an integral part of the Catalan identity that they are recognised on the Unesco Representative List of the Intangible Cultural Heritage of Humanity.