The British Library did an amazing exhibition of maps over history with their role in politics and propaganda a while back. My favourite was a bit of middles ages bravado that was about 3x3m, with meticulous detail, showing one country having completely swallowed another, this was was sent to the king of that country as a warning. The book of the exhibition is still available, I highly recommend it. http://www.bl.uk/magnificentmaps/