Borg installation linking thousands of transwarp conduits across the galaxy, destroyed in Endgame as Voyager used it to reach home.
The transwarp hub was a Borg installation hidden inside a nebula in the Delta Quadrant, linking thousands of transwarp conduits that let Borg ships reach distant parts of the galaxy in minutes. It was one of six such hubs.
In Endgame, an older Admiral Janeway from the future brought technology that let Voyager pass the hub's defences. Voyager reached Earth through one of its conduits, while the Admiral allowed herself to be assimilated and infected the Borg Queen with a pathogen, leading to the destruction of the hub and a heavy blow to the Collective.