Borg transwarp portal

The Transwarp Portal was a large structure of Borg design that was situated in the Regula Badlands.

The Borg Collective used the natural disturbances of the badlands to help in the formation of a powerful transwarp conduit that allowed the Collective to send fleets of ships to assimilate the forces of the Alpha Quadrant.

The Portal was briefly captured by the Federation where it was used by Starfleet to engage in deep strikes against the Collective in the Delta Quadrant. After several operations were made against the Collective, the Federation fleet attempted to retreat back to the Alpha Quadrant, however, the portal was destroyed before all the ships managed to escape leaving several Starfleet vessels stranded, far from home. (TNG video game: Armada II)