What mysteries lurk beneath

A look down into a shaft below the Hoover-Mason Trestle at the Former Bethlehem Steel blast furnace site in Bethlehem, Pennsylvania.  The steel company ceased operations at the Bethlehem plant in 1995.  

Technical details:
Nikon F2 Photomic 35mm film camera.  Nikkor 55mm F3.5 Micro AI lens.
Ilford FP4+ 125 ISO B&W film shot at ISO 250.
Developed in Diafine for 4 minutes (part A) and 4 minutes (part B) @ 20 degrees Celsius in Paterson 3 reel tank.  5 seconds initial agitation with swizzle stick followed by 5 seconds of additional agitation every minute thereafter. 
Negative scanned with Epson 4990 on holders with ANR glass.