Minecraft wiki entry for Cave, associated text: Connected caverns are large, spacious caverns that is usually the result when multiple small caves merge with each other creating a large, messy, single cave. They are similar to large caves except more messy and spacious, with different layers. These connected caverns usually have waterfalls or lavafalls coming out of the cave ceiling, sometimes even both. They also have different "floor layers", meaning the cave has different stone layers that can be accessed to each other in the same connected cavern, simply by stacking up blocks. Connected caves usually have two to four layers. Usually, small regular cave systems nearby eventually connect to a connected cavern. Caves may connect to a connected cavern from any direction, including from above. Connected caverns are not significantly rare, but can still prove to be a small challenge to find.