It's actually a tradition there. Building Human Castles and to be honest it's really fun to watch and dangerous to be in, especially if you consider what happens when everyone tumbles down on you. However, I loved the video ending and especially the Modern Rambo. He looked cool, the kids at the top were ballz (if that's even a word). I wouldn't even climb up and these kids just went up in a flash. It just goes to show you can have some great fun doing some really ordinary things.
If you ever go to Spain make sure to check them out. Post videos of Castellers if you can.
Oh, in India Human Castles are build in the festival called Hooli. And in Pakistan, well they do it in the villages as well but nothing as intricate as in the video. Same goes for India.