"Tres de sis" in our Lady of Mercy festi

Today is the closing of the festival of La Mercè in Barcelona. To celebrate it we have gone to see Castellers at the Plaça Sant Jaume.
We had the opportunity to see this colla (team) lifting a three of six (tres des sis) from below. This means a six-story tower, with three people per floor, which rises, from floor to floor, from below, driven by the bulk (pinya) from the ground.
I've never seen this way of lifting a castell before. It is a very delicate operation which threatens the entire team and that was thanked with a great applause.
You can see in the backround of the picture the city authorities, and Mr Trias, the pressident of the Generalitat of Catalunya (the local autonomic government)., the Mayor.
The building is the Town Hall.