Underground Abandoned Fortress

With the new cave update I would love to see underground structures. One idea could be an abandoned fortress with small stone bridges over long, deep, trenches and wide stairways spiraling down, stopping at various 'floors' where monsters will spawn. It would be like a dungeon of sorts and eventually would lead you down to a room with chests containing random loot. I would love to see this included so caves can be even more exciting and the world of Minecraft will feel like there's more history to it.