The Festival de Otoño bills itself as:

one of the most important theatrical arts events in spain

It goes on for around 5 weeks and features national (Spanish) and international acts from around the world who perform theatre, dance and music. The event kicks off on the 11th October and runs until the 9th November, 2006. There is an English version of the website which is probably better than the Spanish – it uses plain html rather than the damned, annoying Flash!