"Castellers" from Catalan doing what they do best. (More as usual at wikipedia). This is a great photo of one of the towers, most are from below so you can't see the structure of the base. (Thanks to oddee for it). The base has always been the most interesting part of the towers to me, where up to 300 bind together into a locked mass to support those in the tower above. It reminds me a little bit of gothic tracery in rose windows, like this one La Sainte-Chappelle in Paris.
