The Onu-Ta-Le-Koro Subtransect is an underground highway network.
The Onu-Ta-Le-Koro Subtransect lies completely underground, originating from Onu-Koro as a linked series of highways, traversed by foot or Ussal Crab.
The path leads south out of Onu-Koro, with a branch in the left side of the tunnel appearing almost immediately leading to the Lightstone Cavern.
Slightly further south, the path diverges - the left path leads to the rest of the Subtransect, while the right path leads to the surface, where the road becomes part of the Great Mata Nui Highway that leads through Ko-Wahi.
Much further south, the tunnel branches to the left again into the Ta-Koro Highway. Heading eastward underground, almost directly below the North March, the Ta-Koro Highway twists and turns to avoid lava pockets underneath the Tren-Krom Break, before the path emerges on the surface, outside and directly to the south of Ta-Koro.
The initial tunnels were nearly featureless, dark and small - just big enough for two Ussal Crabs to squeeze past each other. The tunnels have since been 'renovated,' receiving ample lighting, expansions and structural supports, and proper markings, though they are kept simple enough in design to allow for further renovation.