The castles were held on the first Sunday of the week of Santa Tecla celebrations. I don't really know who Santa Tecla was. Edward told me once that she came out of the sea and killed a giant spider, losing her arm in the process. I think he made that story up.
The official guide to the festival is delightful but not very helpful. The description of the castles is as follows: "From the last third of century XVIII Santa Tecla has welcomed the best local gangs and they have reached constructions up to nine levels or floors of people like in the mythical celebration of 1881 when it was reached the four of nine without support and the three of nine without support which were performanced respectively by the gangs. At the end of the performance it will be served a vermouth and aperitive with the typical musicians which go always with the humans towers and cheer them " So there you have it.
I have to go back next year, if only to get a new offical guide and to see if I can find the vermouth.
Comments
http://gbgm-umc.org/umw/corinthians/theclabackground.stm
But no mention of spiders, I'm afraid