At some point as a kid, I was dreaming when I suddenly became vividly aware of how odd it was that I would just teleport from place to place when I slept and it upset me. So I dreamed up a train.
Ever since, this train has become a reoccurring part of my sleep. Because of the geographic nature of having an organized transit system in my dreams, it also works as a landmark which has allowed me to map out where different reoccurring locations are in relation to each other. It’s an odd system, but my dreams have become much more vivid and memorable because of it.