Civilization V: The Celtic Chronicle, part 3 (520 A.D. to 1450 A.D.)
580 A.D.: France and the Celtic Republic sign an open borders pact, allowing eager PC Elitist missionaries to begin preaching to the French.
Later that year, word arrives that Hinduism has been founded across the sea.
Unless I've lost count, that brings us up to five major world religions. Hinduism, which I've nicknamed "Zyngalam" after the casual/Facebook game developer, as well as Christianity (Nintendoism) and Buddhism (Sonyism) are still separated from this continent by impassible ocean tiles that can only be crossed when someone researches more advanced naval technology. Still, being a coastal nation, I must be ready to contend with them.
Sweden and France declare joint war against Russia, beginning the Great Southern War.
625 A.D.: London, long the most staunchly English city in the Republic, becomes the last to accept PC Elitism as its majority faith.
670 A.D.: While their French and Swedish allies are tied up fighting Russia, the Germans declare open war on the Celtic Republic, with Russia quickly following suit. The Great Southern War escalates into a continent-wide conflict over land, country, and faith. The King and the Celtic Senate elect not to press the attack, and begin preparing to defend against German invasion.
Germany is on the east coast of the continent, over a dozen turns away, and they have to either cross through allied Sweden (which would be taken as a declaration of war), or the barbarian-infested, inhospitable tundra to the North to reach me. I should have plenty of time to build and station forces to fend off an attack.
I'm not even worried about Russia; they've been fighting the Swedes and French 2-on-1 for several turns, and would have to break through the French lines to get anywhere near me.