I got to say, it always amazes me how many cool, beautiful things there are beyond the confines of my little world. It's an amazing cave, and the view of the world outside through its mouth is spectacular. It really helps to accentuate the sheer size of the cavern, and is a wonderful contrast.
In addition, to match up multiple exposures without having used a tripod to use them is quiet the work, and I'm impressed. I've tried this at times, and even propping the camera up on something hasn't ever really worked out as intended.