I've been meaning to note and apologize for the lack of scale in most of this set of photos. There were two issues: first, we were to stay on the marked paths, and many of the shots were of features that were out of reach. Second, as with any cave, you don't want to touch anything unnecessarily. Oils, salts, bacteria and other "alien" materials to these fragile environments can contaminate and cause damage to them. Another issue related to the latter point has led me to the conclusion that I'll probably not ever tour a cave again. My balance has become unsteady, especially if I don't have strong visual and tactile guidance from my environment. There are rails in many areas, but in the dim light in areas without them, I had a difficult time maintaining equilibrium without grabbing something. I often resorted to bumping things with my fleece-covered elbows to avoid actual skin contact and to establish my orientation. I was borderline uncomfortable through most of this tour.
I'm pretty sure what we're looking at here is a fault surface, with slickensides a bit off horizontal, up on the right and down on the left. There are also two joint/fracture sets, one nearly vertical, dipping right, and the other, also nearly vertical, dipping to the left. The contorted fabric of the marble, and its beautiful (to me, at least) blue-gray color also stand out.
Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)