We should start with a brief introduction to what Castellers are and the basic terminology. As this is a catalan tradition, all the terminology is in Catalan, although I will include the English transaction between brackets.
Basically a castell (castle) consists of a human tower with can have up to ten levels high. These castells (castles) are built during town festivals. At these festivals, different colles castelleres (teams) compete to build the most impressive castell. These colles castelleres dress up in traditional catalan costumes.
Barcelona’s colla castellera (team of castle builders) is Castellers de Barcelona and this year they celebrate their 40th anniversary.