The Labyrinthine Worlds are nine planets known to the Hegemony to contain a mysterious complex of underground tunnels. Five of these worlds are within the Web, the rest are in the Outback . Not created by any natural means, the tunnels are hypothesized to have been carved by an ancient race named the Builders by the Hegemony.
All nine labyrinthine worlds share a set of common characteristics:
- Earthlike - at least 7.9 on the Solmev Scale
- In orbit of a G-type star
- Tectonically dead
- Labyrinths typically 10-30 kilometers deep
- Cross-sectional measurements of 30 meters square