Stone stacking, or rock balancing, is a meditative practice that has become a creative art form. On the meditative side, it involves finding the center of gravity of each of a wide variety of stones, then balancing them atop one another, sometimes precariously. This is the case when large stones are balanced on smaller ones. It requires a lot of focus, and sometimes multiple people.
If the stones just gradually get smaller from bottom to top, it is likely an art exhibit. That cave is clearly done for art based on the number, general size, shape, and colors of the stones used.
