The dungeon is "Jubithiva's Den" and directions to see the second area that I cannot reach are simple. As soon as you come into the dungeon, turn right and go through the door you're facing. This comes out in a huge room identical to the big one with the skeleton in the first dungeon. Go down the stairs you're at and turn left. Walk across this raised area and then turn left and go up the stairs on the other side and into the room. On the wall to your right is a door leading into a dead-end room. If you face the north wall and jump and/or climb and fall on the north wall of this room, you can see a bunch of tunnels and things that are unreachable. I have even used the cheat to warp around the dungeon in an attempt to get into this area, and all of the warps are in rooms that I have already visited! I can post screenshots if needed. Thanks for the help!