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.
The structure of the castells varies depending on their complexity. A castell is considered completely successful when it is loaded and unloaded without falling apart. The highest castell in history was a 10 floor structure with 3 people in each floor. In 2010, castells were declared by UNESCO one of the Masterpieces of the Oral and Intangible Heritage of Humanity.
Here is a gallery of the 26th Human Tower Competition in Tarragona, Spain by Chief Photographer for the Associated Press in Spain and Portugal Emilio Morenatti.