Ideas...

I like the idea of abandoned buildings or generally places which have gone into disrepair, left to their own devices where plants and nature slowly take the thing apart.

http://www.derelictplaces.co.uk/ -

http://www.derelictplaces.co.uk/main/showthread.php?s=2d5167ba285468fcbce1ba82a9ddb48c&t=20222

- pill boxes - all over the place, usually left alone because they're not particularly interesting structures, but the idea of the just being in the middle of nowhere and the thought of their original purpose, as defences in ww2 for the anticipated German invasion.

http://www.pillboxesuk.co.uk/