And she comes to the stairs: great broad endless stone ones they are, and they pierce down far into the world... The spiral stair is wide enough for ten, thirty, a hundred men abreast. There are no safety rails on the inward edge, and the outward edge is solid stone and earth; at the center of the stair is an empty shaft that runs far, far, far deep down, and there seems to be a dim red glow somewhere at the very bottom.

It's an amazing excavation: by any reasonable standards, something that it seems like it would take the entire course of human history to properly carve out of the ground.