...and into a large underground chamber. Fortunately I was not harmed. Unfortunately, I appeared trapped.
How to get out? This appeared to be the ruins of an old tunnel system - despite the cracks in the retaining wall (below), or the brick wall that abruptly ended (above), substantial effort had gone into this tunnel, which suggested there was likely a way out.
A storm drain looked promising...but led only to a dead end.
I discovered excitedly that this was an abandoned coal mine! There had to be a way out. I found a pulley system that was cleary used to haul out heavy objects, likely including the coal. As I looked up from the shaft at the great ropes, I saw daylight for the first time since I had fallen. I contemplated shimmying up the rope, but it seemed so far I dared not ask my body to climb that far unless I had no other choice. I resumed walking.
I found train tracks, and correctly inferred that they would lead to more of the mining operation. Several old coal cars remained underground, with their precious cargo still inside.
I was about to give up, and try the rope I had seen earlier before my strength was too badly diminished. Then I saw it: an elevator. Did it still work? There was only one way to find out. I reached out a tired finger and pressed the Call button.
Gears creaked but moved. Slowly the car moved toward the bottom of the shaft. I climbed in, and the car took me directly to the surface. I breathed a sigh of relief - and vowed to spend more time in the future looking where I stepped and less time at the skies.