On the other side of the tunnel, we see sunlight. Though we are underground, there is a hole at the top of the cavern that is open to the sky. I think its called an oculus. Someone flying overhead would be able to see the city without much difficulty, but from the outside, it probably looks like a mountain.
At least we have another way out, I say, not really thinking about the amount of climbing it would take to get out of here.
Theres a waterfall that flows from the top of the cavern down into the middle of the city, falling maybe two hundred feet through open air, giving a very peaceful subdued roar to the ambient sound of the city. The waterfall ends in a lake at more or less the center of the city. Its easy to see how this place started out as being built on the shores of the lake, and spread gradually outward to fill up the area.