321
When you press the last button in the sequence, you hear the locking mechanism disengage and the bronze portal slowly swings open. You hurry through, pausing for a few moments to pull the heavy door shut behind you.
The tunnel continues and you follow its central wagon track as gently it descends through the ore-rich rock. After several minutes, you detect a noise like distant thunder rumbling in the passageway ahead. You proceed with caution now, and gradually this low, thunderous noise becomes a series of individual bangs. Soon you catch sight of a lantern-lit hall in the far distance. When you stop to magnify your vision, you see at once that it harbours the source of these loud explosions.
