Castle Base (Earth-5875)

Castle Base was an underground facility of the Office of Naval Intelligence, deep underground the Reach FLEETCOM Military Complex, in Csongrád, on Reach. Constructed two kilometers underneath Menachite Mountain, Castle Base was massively protected by reinforced concrete, granite, titanium-A armor plates and EMP-proof metals.

History
Dr. Catherine Halsey and Colonel James Ackerson had a personal office within Castle Base. Some of the training undertaken by the SPARTAN-IIs occured within their base, allowing them to grow tirelessly familiar with the territory.

During the Fall of Reach, the base served as the fallback position for Red Team's Delta division, consisting of William-043, Vinh-030, and Isaac-039. The trio was then joined by Fred-104 and Kelly-087, who later discovered Dr. Halsey, who had remained operative under Operation WHITE GLOVE. Her directives were to destroy the base and prevent the Covenant from acquiring technologies being developed by the UNSC.

The Covenant eventually located the base and attempted to invade it, forcing Halsey to activate WHITE GLOVE, leading to Castle Base's destruction and the deactivation of her Auton synthetic Kalmiya, stopping the Covenant from acquiring vital UNSC data. Halsey and the SPARTAN-IIs then retreated to the dangerous titanium mines found below the mountain, eventually encountering a mysterious complex.