My take on the Skynet Pyramid from The Terminator franchise
Skynet Central Core Skynet Central Core, also known as Skynet Core or Skynet Central Processing Center, is the facility housing the Skynet's mainframe.
As Skynet was originally built by Cyberdyne Systems Corporation for Strategic Air Command - North American Air Defense (SAC-NORAD), the Skynet Core is located in Cheyenne Mountain, Colorado, the base of SAC-NORAD, which is the world's most heavily-armored and defended mountain. Hollowed out, reinforced and armored, Cheyenne Mountain is capable of withstanding a direct hit from a nuclear missile. This made it the perfect installation at which to build Skynet's mainframe.
Heavily-armored and fortified, Skynet's Central Core Installation at Cheyenne Mountain was guarded around the clock by squads of Series 800 Terminators with patrols of Aerial Hunter Killers and Hunter Killer Tanks, and was defended from large scale rebel assaults by massive Phased Plasma Cannons.
Skynet's Central Core was located deep underground within Skynet's main complex. From intercepted surveillance of video data feed, the Resistance was able to hypothesize that this Central Core was a form of cold fusion reactor, needed to supply Skynet with its tremendous energy requirements. This Central Core is the key to Skynet's ability to operate; Skynet would be rendered virtually disabled without it. It has therefore become the main target for the most skilled Resistance strike teams. The Central Core is protected by the T-1000000, and thus there have, as of yet, been no successful strikes against it