Before the builders came, there were the walkers.
The walkers moved through the city at night, not the city that stood, but the city that waited underneath it. They said: every place that has been lived in long enough becomes two places. One in daylight, one in sleep. The daylight city is impermanent. The sleep city is the one that remains.
They kept their maps in small books, the writing sideways so it could be read in any direction, because the sleep city had no fixed orientation. Its streets met at angles. Its quarters had no names. It repeated the landmarks of the daylight city at slight variance, as if the memory of the daylight city had been used to build something else entirely.
What did the walkers do with their maps? They compared them. At a certain hour of morning, before the city woke, they gathered in whatever corner of the sleep city they had in common and they confirmed: yes, I also have this. The fish market district. The square with the large tree. The street that ran parallel to the river but curved away from it in a way the river did not.
These they recognized across their separate maps. These they confirmed.
They were not the last people to keep such maps. They were the first people to know they were not alone in keeping them.
A student of theirs wrote, and the writing survived in the form of a single copied page: I have heard it said that the sleep city is a copy of the waking city. This is wrong. The waking city is a copy of the sleep city. The builders build toward something they half-remember. This is why no city is ever quite finished, and why no city is ever quite where you expect it to be, and why the place where two streets should meet never meets precisely the way you thought it would.
This, he wrote, is the cost of building from a dream.