A Mighty Stairwell

You head into the squared-off tunnel. Tool marks on the wall confirm your suspicions: this tunnel was dug out by someone. The tunnel ends abruptly, opening into a tall, open shaft. It's a long way down, and a long way up from here as well. This must have taken immense effort to dig out!

You are standing on a sort of balcony with stairs on either side. The steps lead up and down a spiral staircase carved into the wall of the shaft, snaking away into the darkness. It seems ancient, but the stout steps are in good shape.