A city I made for Survival mode (preferably) and in Medium or Hard (again, preferably). You can play Survival, where you must survive against zombies, spiders, creepers and skeletons. Or you can play Adventure, where you must survive against zombies, spiders, creepers and skeletons, AND find all of the keys to find the antidote!
You are stranded on several islands (more than three) and you must fight with limited resources. It is to be played on Hard mode on Survival. I didn't make it, I just pressed create new world and this was where I spawned - all I did was add a tree.