Castells are a Catalan cultural phenomenon, a human tower (torre) built by competing colles representing a different district of Catalunya. The process is precarious and intense, with dozens of Castellers pushing on one another to form a steady base while others climb and form the tower, finishing with the smallest (and youngest) to cap the structure and raise four fingers in the air to signal the tower is complete. The structure is then carefully disassembled all while being urged on by supporters and an accompanying band of musicians.