I wonder if the cave I'm in will link up to either of these! The one I'm in is kinda close to the pirate ship. Last night I bricked up the waterflow into a big chasm that had some lava in it. I'll start checking the chasm out tonight or tomorrow.
At one point I found a dead-end hallway with FIVE creepers! I really wish I'd had a bow to kill them with, my plans for the Observation Deck involve TNT.