human
Make a concise location description of a foreboding tunnel passage with a portcullis, door, and torches.
assistant
Thick stone walls have been fortified with steel beams, making this tunnel as much of a fortress as an ingress. Its entrance bears a raised portcullis, allowing travelers to come and go freely, but serving as an inconspicuous sentry in case of need. Torches are mounted on alternating beams, burning brightly to join the moonlight entering from the opening. As the tunnel spirals downward, the torches cast shadows on the walls as the corridor ends abruptly at a heavy iron door.