The Cistercian monastery of Poblet is one of the more interesting and impressive buildings I have been to. The fact that it houses the tombs of a long line of kings and queens of Aragon in a great pantheon makes it especially noteworthy. Anybody coming to Catalonia should try to visit Poblet, located in the hills northwest of Tarragona, since you will hardly ever come across a better monastery anywhere. Having said that, however, you should either have a private car or join a bus tour, since reaching Poblet by public transport is very inconvenient, to say the least. I didn't really mind the 4-km walk from the nearest train station, since the weather was great even in late October, but I don't think many people would do the same (and there were hardly any signs).