Wow! I've had comments. Thank you Choco and Lasgunpacker. It's nice to know that some of the things that I am thinking about have struck a cord with you.
So to keep a good thing going I have collected a big pile of polystyrene that I can use to build ruins. I need to think about how I want to divide up the pieces I have. I don't want to ruin them by making trash decisions. Planning and preparation is the key to a project like this. One piece is already broken which is a bit a of a shame. I'n sure I can work around that though.
I need to think about how I'm going to cut this polystyerem up. I might use a saw. Or i might use a bread knife.
I've also found out that this isn't normal polystyrene. This is expanded polystyrene. I wonder if I'll be able to get a hold of any no-expanded polystyrene for building ruins with? Can anybody point me in the right direction?