A mandatory safety precaution brought in (to the disgust of some diehards - maybe not the right choice of word here) after some nasty incidents maybe 20 years ago or so.

It is one of the most impressive feats of collective endeavour I have ever witnessed.

There is an annual competition held at the bullring in Tarragona (the region where the tradition is most deeply rooted), which is quite something - the whole arena full of the different teams each with their different shirt colours, one tower going up after another, with a commentator over the PA telling everyone which particular formation (number of levels, and number of people on each level) each group has successfully completed, by the child at the top raising their hand and holding the pose steady for a second or two, like a weightlifter.

Definitely worth trying to catch if in Catalonia.

Bear in mind, though, that 'castell de foc' listed on the programme of events is a traditional firework display, nothing to do with either correfoc or castellers.

The festa major in Girona in October also ends with a correfoc - I wrote about the preceding funfair in this article:

https://medium.com/ellemeno/the-most-magical-funfair-in-the-world-ff4638bce533