If you go to x-350 z1000-ish you'll find some massive, awesome looking mountains with multiple layers, floating islands, and even a dungeon above the clouds! The dungeon is a skeleton spawner at x-332, y 135, z 1017. Inside is some horse armor, a music disk, nametag, and two saddles, among other things. It's quite a ways from spawn, but it's worth it. The dungeon in the picture is lit up with torches.