The Tower, as it is called by the biologist of the 12th expedition, is a structure of unknown origin and purpose located within Area X. It is a hollow cylindrical structure embedded in the ground, with a flat circular top protruding several inches from the soil. A rectangular opening on the top leads to a spiral staircase, which fills the entirety of the tower.
- While The Biologist prefers to call it "Tower", most characters mention it as a tunnel.
- The Tower and the Lighthouse (most prominent structures in the Area X) seem to mirror each other: a cylindrical lighthouse extending into the sky, and the similarly-shaped "tower" that extends into the ground, both of which share a common caretaker.