Building human towers, called castells, was first documented near the city of Tarragona, Spain in the 18th century . A Catalan cultural tradition, the practice spread throughout Catalonia during the 18th century at local festivals, which opened the door for competitions. With teams called colles, the goal during a competition is to successfully build—and deconstruct—the highest and most complex human tower without tumbling. A small child often tops the tower. In 2010, castells were declared Masterpieces of the Oral and Intangible Heritage of Humanity by UNESCO .

There are a number of colles, including the Castellers de Vilafranca , which was founded in 1948 and has over 400 active members. In November 2015, Minyons de Terrassa became the first colle to successfully build and dismantle a "4 de 10," a tower's height that measures ten groups high, with each group consisting of four people. Surprisingly, accidents are a rare occurrence while building castells, though a 12-year-old girl died in 2006 after falling off of a castell. Before the 2006 fatality, the last fatal accident was reported in 1983 .