Catalonia, Spain - human towers made for the Concurs de Castells (Competition of Castles) held every 2 years.
Christian and I saw a few groups building these human castles when we were in Barcelona in 2009. It was an inspiring day in the streets - we stumbled upon a street festival (not the first time!) where we witnessed this courage, strength, trust and bondedness.
See the rest of the photos and a bit more story on Bored Panda.