I can thoroughly recommend climbing if you're unfit and want to ache all over all the next day. In fact, the Castle is perfect if you do some of these, and one of these [larger photo].

I've never felt anything like it. You're a few metres off the ground, standing on one leg balanced with your hands and reaching as hard as you can with your other foot. You've got a rope, you're not going to fall... but it's so real. Reaching the top I realise there was music on and people around and all the rest, but my mind has been blank, completely on the moment. In the moment. It feels fantastic; I was shaking (although later because I was over-reaching and just got fatigued). I want to do this again.