Ruined cities and ancient battlegrouds.

I think there should be a new, super rare structure called the ruined cities which would have housed the ancient civilisation that inhabited the overworld.

They would be bigger than ancient cities, but will be in the overworld and filled with the undead. They would be in a medieval style, with a crumbling castle an decaying city walls. They could have libraries (maybe with a history section where only a couple books survived?) and barracks with chests with weapons, armour stands with armour and beds with chests containing personal items (including maybe diaries?), both guarded by undead librarians and soldiers? Maybe it could contain half finished versions of a new golem that the community needs to figure out the recipe for? Talking about soldiers, how about ancient battlegrounds, where they fought their enemy? it could contain small outposts, maybe even bunkers. it would cover the same amount of area as an ancient city (but without any actual large buildings other the outposts or bunkers, as well as being flat and desolate). they would be about as common as villages and will be full of undead soldiers, as well as regular undead. they could be full of random tnt explosions, skeleton skulls and maybe swords stuck in the ground, as well as being full of random blocks of tnt with pressure plates on top.

Also with the books, it could be written in a strange language the community could figure out, maybe with clues hidden in the cities. The update could be called The history update.