One of the largest structures in the Neverous Ether is believed to be The Coil, built by a group of future-humans who call themselves the Cerebellum.
The Coil is a long, twisting tunnel that that winds through the Ether itself and features rail-based transportation between worlds.
It is not known how the Cerebellum created the Coil, or how it works. It appears as nothing more than a thin filament in the Colourful Vastness.
Michael Scott Hand 