Minecraft wiki entry for Elevators, associated text: Combining the drop shaft with a bubble elevator can be done with them touching at the corners of the shafts for a 2x2 block square vertical up/down the shaft for deep mining. Looking at the 2x2 block from a diagonal, put the drop shaft at the 'front', glass or fence at the two side blocks two blocks high, then the bubble shaft at the 'back'. You can fall through the drop shaft, walk out, then walk through the drop shaft into the bubble column to go back up.