I have argued time and again with my friends, that Victorian London would be the perfect next setting for the Assassins Creed series. Brilliant architecture to climb on like Big Ben, St Pauls etc. A complex political background including the British Empire, invention of the police force, independence of America and it's following civil war, Jack the Ripper, an industrial revoloution. You could have Charles Babbage, the mad inventor of the world's earliest computer, as a Leonardo-type accomplice. I'm sure there's more, but you can probably get a very good game out of that.