Here's an idea I had on another thread about how religion could be brought back to civ5 in an expansion pack. City states - such as Jerusalem, the Vatican, etc. - could found religions (instead of civs) and become holy cities that attempt to spread their religions. This could either be 'accurate' - e.g. the Vatican founding Christianity, Jerusalem founding Judaism - or random. (For cities like Mecca that are already in the game, they can be renamed ) It has already been said that city states will care about your social policies but other civs won't. The same could be true of religion (i.e. adopting their religion will make city states more friendly towards you, but other civs won't care that much). That would avoid the problem in civ4 where diplomacy was too religion-focused, and it would also stop the race to found religions. It could also lead to some interesting requests - e.g. the Vatican asking all Christian civs to join a crusade against another religion or holy city. Discuss. EDIT: If you are looking at this thread for the first time and don't fancy reading through all 9 (at the time of writing) pages, Col Mustard has put together an excellent summary of the best suggestions so far here.