h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I'll put in a mention for Cardiff Castle in the hope that someone else can add a bit more to this entry.

Cardiff castle is situated in the town centre of Cardiff so isn't difficult to reach. There is Student discount for entry and there re two different prices for what you can go an see. From what I remember, I could be wrong, there is a smallish fee that allows into the grounds so you can visit the teashop, the military museum and look at the various types of cocks and chickens in the grounds. The higher fee allows you to see other things but I'm not sure what as I've never done it.

PS - I think they used to hold rock concerts on the castle grounds. Acts have included Simply Red, Bryan Adams and Bon Jovi. I'm not sure if they still do concerts there since the building of the Millenium stadium.