The Great Underground Highway is a system of toll roads stretching throughout both the Eastland and Westland provinces.

The standard Highway toll is one zorkmid, but tolls can run as high as Zm 3 depending on your point of departure. Toll gates are usually manned by hired gnomes.

To date at least four branches of the GUH are known to exist: Number 2, near Egreth, goes from Bozbarland to the Glass Maze; Number 90 runs from the White Cliffs Beach to Port Foozle; Number 95 spans an immense distance from Flatheadia to Fublio Valley; and one branch even extends all the way to the Gray Mountains.