Minecraft wiki entry for Shelters, associated text: Using this gives you a chance to find resources, and in the case of invasion by mobs, it will always provide a safer spot. Underground floors are also useful for making mob grinders or animal farms. If you're really good, add a whole back up shelter under ground. If you like to be safe, add multiple bunkers, but hide a super safe and secret bunker. You could also make a part of the floor out of glass in the same spot on each floor, so you can see all the way down, and it looks nice if you do it right.