Initially, there weren't all that many doors to check. The corridor had no side offshoots and turned off sharply to the right before too long, then left, left again, and right once more after some more time before it seemed to reach the inner structure proper. Lamps in the ceiling provided warm yellow lighting to the hallways, and though the suits impaired your hearing of external sounds, you thought there was even music playing in the background.
Eventually the corridor brought you to an intersection, a small room with corridors leading out in four directions. It even had some quite large tropical potted plants in the corners. While you were pondering which way to go, however, you saw something approaching down the corridor to the left of your entrance point. It was far away for the moment, and looked like a shiny bronze sphere perhaps a foot across, hovering casually in the air. It didn't seem in any particular hurry to close with you, but it was approaching at what would probably amount to a calm walk if it had legs.