I was in a pretty large well-lit cave on the side of a mountain. There were some other people there too, but I don’t recall any particular interactions; I was mostly involved in just exploring it. I was observing the internal surfaces and noticing how the ceiling was quite flat and smooth in large sections, quite rectangular and level, nearly parallel to the ground, with somewhat of a slope. I wondered why there was an absence of rubble or loose dirt or rock in this cave, since I had imaginations about guys blasting or picking away at the inside, then shoveling the pieces in order to remove the material. Then I saw a small section off to the side which caught my eye because it seemed like there were unique objects placed there, as a type of designated area where excess material had been accumulated but not yet dealt with. I was curious about these items because they appeared unique, but apparently believed to be of no particular value to everyone else. So I went to get a closer look, perhaps I’d find a keepsake or something to remind me of what was naturally here before all of this artificial treatment.
The first thing I spotted clearly was a cylindrical shaped clear tube, which was like a thin-walled, extremely tall, uniform width beer glass, about about 4” wide and 24-30” long. This was in contrast to another piece I saw laying down off to the side which was a similar shape but I suspected was solid crystal and still embedded in rock. It was interesting stuff to be just getting ready for disposal, but I suspected it was just a byproduct of the major objective which was clearing out the space, smoothing the surfaces, making more internal/usable volume inside the cave. So then I looked back toward the rear of the cave and saw an interesting pattern of relief on the ceiling, which had a jagged overhang that had a very distinct, artificial-looking form, because of the consistency in the surfaces, it looked machined. It was rock and appeared somewhat natural, but the ridges were shaped deliberately. This overhang was almost like a vertically hanging stub-wall which delineated the space between the back and center portions of the cave. The rear portion was more spherical, and this ceiling formation sort of rounded with an arc that made it a type of perimeter between the back and the middle, where I was standing. Then suddenly someone threw a chunk of food toward the opening/front of the cave, where I could see some outside light coming in. I wondered about what kind of animal whomever was intending to attract with that, or if it was a joke or completely careless, but suspected it was likely a bear would find it.