Participants make human towers or "Castellers" during the Saint Merce celebrations in San Jaime square in Barcelona, Spain, Monday, Sept. 24, 2018. 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. (AP Photo/Emilio Morenatti), APTOPIX