misc. 25 underground city

I was at an old house in its basement and in between a couple of rooms was a wall, but there was a big hole there ,easy for even tall people to walk threw, so I walked threw it and it was a long dirt road that went along a side of a barren mt. Looking hill and as I looked off the steep side i could see an entire city right before me as if a ghost town had been left down here because there were no other people around and it was super dark, but some how I could see in the dark