As the balls float into the passage, it brightens up. The end of the passage is still unseeable.
Stalagmites and Stalagtites reach for each other all the way down the natural cavern, other than the 15' circle you are in currently. After the circle directly under the trapdoor, the cave drops just slightly. Behind you, the other way, leads into an extremely deep pit, from which a sound similar to grinding gears can be heard.