Every two years in Barcelona, in northeast Spain, a competition for the tallest tower of the people (de Castells human towers). Approximately 42 teams, numbering up to 500 people, building a design of human bodies in 10 tiers. Teams compete in five rounds, points are awarded depending on the difficulty and height of each structure. Sometimes the "tower" capsize, the participants get injured. About 20 000 spectators from around the world come to see the show, which is included in the cultural heritage list of UNESCO.