My world includes a huge underground mine, a workshop with 5 chests, a crafting table and a furnace, a volcano that you can go inside that houses a nether portal, a wall with a gate that has a quad door using a redstone circuit I designed myself, a dock, a large tower that you can go up in to look at the world, and a mob spawning and trapping system. In the nether, there's a castle built on a lava lake.