Wanted to provide some more information here on the cave that many seem to have found and others have missed. It's located quite close to the junction of the blue trail and the jeep path that goes to the main parking lot, and is right before the steep rise of the face of the mountain. It had a stream running through it and the trail actually went over the cave forming a natural bridge. I found it was easiest to access from the north side of the blue trail, and after climbing down into the sink/pit the cave had formed, you encounter the stream flowing through. The stream continues to the right, off into some unknown fissure that I didn't explore but could be possibly squeezed into. Going to the left up a slight crawl, the cave opens into a sizable room which I could stand in. It is decently dark so a bright waterproof flashlight or headlamp is handy. The stream flows into this room by a waterfall which was right at the end of the first sink where the stream dips underground. You could climb out this end but it was pretty steep and slick with the wet rocks.

The cave was cut through dissolution of the marble rocks, in much the same way as a limestone cave, and revealed some interesting features of slate layers and large quartz crystals within the rock from the metamorphosis of the marble. Marble caves are quite rare as compared to their limestone counterparts, and this is certainty an interesting place to explore not far at all from the trail.