Minecraft wiki entry for Shelters, associated text: Once it is light enough, and the undead have burned, simply dig out the blocks you're perched upon, until you're back on the ground. (Check for nearby creepers and other monsters first!) Don't just jump off your tower unless there's water below you – if you're high enough to avoid mob detection then you're high enough to take damage if you jump, or even die if you're 22 blocks or more up. Also keep an eye out for spiders, which can meet you halfway and knock you off the tower. If a creeper is hanging out at the base of your pillar, and you have more blocks, try going even higher—30, 40 blocks, or even up to cloud level. This makes monsters on the ground despawn far more quickly (because they are now farther away from you).