The circuitous paths taken by light into caves produce the famous alien scenes seen in, for instance, the slot canyons. From the outside, the caverns are totally enshadowed, but from the inside looking out, the gradient in light levels from black deep inside to white outside reveals a much more interesting scene.
Last weekend I made it to Pinnacles National Park (two hours south of the Bay Area) for a few hours, and experimented with some similar cave entrance photography in Balconies Cave. Though the cave was far from empty, I found a scene looking out through the north entrance that was free of cavers. Visually, I think this scene is really striking. The rocks around most of the image are in near-silhouette and serve to frame the scene. Usually I like paths in images that the eye can follow into the scene, but this scene has almost no depth. The path is upward into the light and out of the scene entirely. Further, the rock placement is very puzzle-like, and epitomizes the story of the formation of Pinnacles by intense volcanic and tectonic activity whose radical jumbling of the rockscape endures to this day.
I’ll have to explore Bear Gulch Cave (closed this visit) next time. The outdoor scenes are also impressive, but the gloomy overcast skies stymied outdoor shots on this trip.