This system of halls and chambers is formed almost entirely of high-grade crystalline quartz. The walls and ceilings are faceted and are made up of thousands of large conjoined crystals. The floor is mostly just a rough and irregular surface of broken crystal, but there are places, especially alongside the walls of rooms, where many sharp crystalline points still poke up making a surface with very difficult footing.
There are a range of colors in the rock of this place, from purple and indigo through to pale yellow. Deeper colors are less transparent and harder to see through. However, because of the numerous facets and the crystal structure of the rock, none of it is very glass-like in terms of being able to clearly see through.
The ‘bridge’ (where the two hallways cross over each other near the entrance) is a clear quartz so that torchlight from a group passing by would be readily noticed by someone in the other part. Some of the walls are thin enough and clear enough that this is possible in between other adjacent spaces, as well.
Although this is not stalactite and stalagmite structure, there are many areas with projections of crystal jutting up from the floor or extending down from the ceiling, and the heights of rooms and halls vary widely throughout the complex.
(If you want to think of this like being inside of a giant geode, you are not far off.)
As usual, feel free to use for any non-commercial purpose, or contact me if you’d like to use this on a commercial project.