Heavy Metal Structure

This was some Kodak Kodacolor-X film I found and developed it. They stopped making it in 1974, so it's on the order of 50 years old. I didn't notice until after I started developing it, but the 126 cartridge said it was C-22 - I used C-41, so I'm not sure how it turned out. It might have lost all the color or the colors could be shifted a lot. But, to me, it was pretty even, except for the top and bottom edges.

I'm not sure what the structure is, but from looking at some other frames, it kind of looked like a coal mine, and it sat next to a railroad line.

Camera: Kodak Instamatic 154
Film: Kodak Kodacolor-X 126 size
Lens: 43mm
Aperture: f/11
Shutter Speed: 1/90th of a second
Date: 1960's/1970s
Location: Unknown

Developing Chemicals: Unicolor C-41
Water pre-soak: 1 minute at 102 degrees
Developer: 3 ½ minutes at 102 degrees
Water rinse: 2 minutes (to keep chemicals clean)
Blix: 6 ½ minutes at 102 degrees
Water rinse: 2 minutes at approx. 100 degrees
Stabilizer: 1 minute at room temperature
Water rinse: 2 minutes
Kodak Photo-Flo 200: 1 minute

Kodak Kodacolor-X 08ff