I have mapped Section UW-7-Delta forty-three times. I have forty-three different maps. They are all accurate. They are all different. The tunnels move.

I want to state this clearly because people assume I mean something less literal than what I mean. I do not mean the tunnels are confusing. I do not mean I get lost. I do not mean my instruments malfunction. I mean that the physical tunnels — stone, concrete, infrastructure, the actual built and excavated passages of the Underworld at depth 7, section Delta — relocate. A passage that runs north-south on Monday runs east-west on Thursday. A junction that connects three tunnels connects five tunnels the next time I visit. A dead end opens into a chamber that was not there before. The chamber is real. It has dust on the floor. It has water stains on the walls. It looks like it has been there for decades. It was not there last week.

I began the Underworld Mapping Project fourteen years ago with the goal of producing a definitive map of the Underworld's tunnel network. I have mapped approximately 80% of the known Underworld to a standard that I am confident in. Section UW-7-Delta is the remaining anomaly. It is approximately 600 meters square. It is the only section that will not stay mapped. Every other section of the Underworld is stable — tunnels stay where they are, junctions maintain their connections, dead ends remain dead ends. Section Delta changes. Not quickly. Not while I am watching. But between visits, which range from three days to three weeks, the section reorganizes itself.

I have placed physical markers — painted symbols on walls, bolts driven into stone, reflective tags at junctions. The markers move with the tunnels. A painted arrow I placed on a north wall is now on a west wall, still at the same height, still in the same paint, still in my handwriting. The tunnel moved and took my marker with it. The stone remembers being marked. The stone does not remember where it was when I marked it. I have accepted that Section UW-7-Delta cannot be definitively mapped. I continue to map it because each map is a snapshot of a place that exists in a state of slow, silent rearrangement, and because forty-three snapshots might, eventually, reveal a pattern. I have not found the pattern yet. I suspect the pattern is looking for me.