Abandoned castle

Structure
The abandoned castle is a naturally spawned structure which contains the Dragon king and other mobs. It is a 70 block tall and 91 block wide castle made out of stone-brick, mossy stone-brick, and cobble stone. It has glow stone in the walls. It also has random gaps in it surrounded by ash.

Spawning
A tower will always spawn next to it. It will spawn in the overworld in plains, and extreme hills biomes. Only one will spawn per-world. Chests whith random items will randomly spawn inside full of treasures.