The two extra nights gave me a chance to see the premier of a documentary film about Catalonian Castell groups called Enxaneta. They create human towers sometimes up to 10 levels high and it is a tradition which has been declared a Masterpieces of the Oral and Intangible Heritage of Humanity by UNESCO. The top levels are usually topped off by small children who are the lightest of the group. The castell group I saw in New York flew 140 members all the way from Catalonia to perform.
Here is a short video I took of them creating a 7-layer tower. Note the music and how it is synched to their progress in the tower. The people on the lower levels of the tower know how far along they are by the progression of the music.