On the edge
I was on the roof of a building in a big city. I could see lights to a very great distance and hear traffic sounds. The building was not very high, only a couple of stories.
I must have been in an old industrial section of a city. All the buildings were of brick and had that prison-like architecture so typical of inner-city buildings left over from the 19th century.
I stepped up on the low rim that surrounded the roof and stepped off. I dropped down about ten feet to a lower roof and crossed it to what I thought was the Northern edge. There I climbed up on the sill or ledge or whatever it is called and made a jump.
I landed on top of a wall no more than four feet wide. A thick wall, but attached to nothing. It was not part of a building nor did it seem to be part of a ruin. I began to walk along the length of this wall (like there was any other option) in what I think was an Easterly direction. The top was rough, jumbled with detritus of wood and large metal pieces. I came, quite soon, to a point where I could see that the wall became just an archway and a crossing street passed under it. It was at this point that I figured out that the wall was nothing less than an old, now unused, support for an elevated train. It was an almost stunning realization. I don't know why it struck me so hard but it was a true thing of wonder to me that there should be elevated trains.
I continued walking until I came to another archway, several streets over, where the keystone and a few others had fallen. The gap between me and the next segment of the arch was about five feet. It wasn't a particularly long jump, but I was very afraid to make it. I dithered a while, backed off a great distance and made a running jump. I landed on the far side well past the gap. When I landed, however, something grated under my foot. It frightened me so, losing my balance that way, that I woke.I went back to sleep immediately and dreamed again. I don't remember the dream or dreams that followed. I woke tired again this morning.