I've gotten interested in ancient, medieval, middle ages, etc. history. The more i get into the more interesting it is (and the more i see how messed up the world has been from the beginning). Anyway. Do any of you history geeks know of a good map overlay 'system'? I'd like to see what constituted Byzantium, how far Genghis Khan and Tamerlane roamed, the Viking travels, how large was the Roman Empire, etc., etc. I'd like to be able to lay over and see how era's have overlapped. Any guidance will be appreciated.