Central nexus

Admiral Janeway and the Borg Queen in the central nexus

The central nexus was the heart of the Borg Unicomplex, from where the Borg Queen directed all activities of the Collective, including coordinating the actions of vessels, commanding Borg drones, and regulating the shielding of the interspatial manifolds supporting transwarp hubs.

In 2378, Kathryn Janeway's counterpart from twenty-six years in the future used a synaptic interface to communicate with the Queen within the central nexus itself, as part of her plot to destroy the Collective. (VOY: "Endgame")