Choose Your Own Adventure!
You decide the large tunnel to the right is your best bet, and start onward again. It's a little dark in here, but not so much that you can't see. Except... it seems to be getting darker. The light from the beginning of the tunnel has long faded, and there doesn't seem to be any holes in the ceiling to let in more of it. You start to move quietly, listening in the dark for other sounds. In the distance, you hear a scraping kind of noise. Do you keep going forward, or head back to choose a different tunnel?