Instead of a pit in the floor, now there is an oversized chessboard here.
This is an elevator to move mine car loads of sand to the surface for cleaning and eventually glass production. Below is a flooded equipment vault. In front and behind is a loop through the larger tunnels in the mine. The horizontal braces supported electric cables for the mine carts.
Short-stack remains of mounts for rod and ball mills, if I was to bet. The concentrator separated junk rock (tails) from the copper and silver ore, to such a point it could be smelted.
This is what it might have looked like if a new Ford descended in the elevator with its headlights on. As seen from the Mississippi side–the opposite portal faces the sand mine.
A broken roof drain turned the fourth floor into a skating rink. Frost covers every surface. Kodak Portra 400 in Voigtlander Bessa.
This picture shows the challenges of moving around underground in the base.
2016. A section of the third floor that has changed a lot over the years. Compare to 2006 shot.
Days after the long-flooded basement was pumped out. Note the water lines!