The cartographer updated the settlement map each season. The town grew outward from the crossroads at the center, one ring of new construction each year, until her grid was filled edge to edge. Then word came from the eastern survey team: the river had shifted its course in the spring flood, swallowing the entire rightmost column of buildings. The structures she had drawn in that column the previous season were already underwater. She whited out the eastern edge and issued a correction. By the next survey, the town had rebuilt on higher ground and the grid was full again.