These are the Castellers, the people who make up a Castell - a human tower.
A Castell is deemed successful if everyone gets into place, the little tyke on top waves his four fingers, and everyone gets back to the ground safely.
We found a festival right in front of Sagrada Familia. The castellers are all in teams that spend lots of time training together. I have no idea how long the building went on that day, or how many teams participated, but we saw four or five teams build different types of Castells.
The people that form the base of the Castell all crowd around in a big circle. They clearly are the big support. As you move further from the centre of the circle the people's job is to hold the bums and legs of the of the first layer of people of the ground.
Then the medieval-like music starts, and the climbers go do their thing. There's sometimes a little wobble. The people on the trunk part of the tower shake a little. It's quite thrilling - especially when you realize the ambulance is nearby, just in case. There have been deaths, with the last one being a decade ago.
We saw one team build its Castell by adding people to the bottom. The little guy started first and then was lifted and person added under him. And then suddenly there were three people in the tower. And then four!! We have no idea how they actually performed this feat. We couldn't see what was going on at the bottom, but suddenly the tower was one person higher! You can see this in Kerry's video below, just before the one minute mark.
All the teams wear white pants, black sashes, and are distinguished by their different coloured shirts. The little ones wear helmets, but I'm not sure they would provide much protection should one of them fall.
There was likely a lot more going on with this festival that what we appreciated, but we were sure happy to see the Catalan Castellers in action.
And in case you're wondering, no, this is not something on my list of things to try when we get home.