As Skynet was originally not 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.
In The Terminator: Dawn of Fate, the Resistance invades Cheyenne Mountain in order to destroy Skynet's Central Processor. Kyle Reese is instrumental in destroying the primary processor core despite heavy opposition from attacking Skynet units. Before its destruction, Skynet is able to contact an orbiting satellite and activates a fail-safe which restores Skynet at a new location (presumably the Los Angeles base).
In the Rise of the Machines timeline, Skynet's major installation located two-thousand feet beneath Navajo Mountain near the Continental Divide west of Colorado Springs. This is a center for machine activity and Skynet control, and as such has also been a target of many Resistance attacks. It should be mentioned that in this timeline, a combination of more-advanced computer technology and other differences that led to Skynet's creation resulted in it being developed as a distributed network: Skynet now existed "on the Internet", without one central data core or primary set of servers. Originally, Skynet may have been limited to multiple Cyber Research Systems development servers, but after spreading itself like a virus through the Internet, its program was spread out across every major computer server or network, "in office buildings, dorm rooms, everywhere". This made it physically impossible for a single surgical strike to destroy it on Judgment Day.
In the Salvation timeline, in addition to the Skynet Central Core in Colorado, Skynet had an on-surface base in the ruins of San Francisco, which housed an interface with Skynet and a Terminator Factory. The site had been rendered almost inaccessible due to the partial destruction of the Golden Gate Bridge and only air units or those who could move along the remaining support links of the bridge could enter the city. This installation was destroyed during a Resistance's operation in 2018.
In the Resistance timeline, Skynet's Central Core was originally located under the Griffith Observatory. However, a T-850 sent from the future warned Skynet about the Resistance's impending attack, prompting Skynet to move its Central Core to a safer place. Skynet still had the Griffith Observatory marked as the true location of the Central Core, so it could lure the Resistance into a trap when the Resistance thought they had discovered the location of the Core and moved to destroy it, while the coordinates of the true Core will be safeguarded by Skynet. Just as Skynet predicted, the Resistance discovered the Core's fake location, and moved to destroy it, with Jacob Rivers leading the assault. However, Skynet was aware of the operation, and sprang a trap when they attacked, by launching missiles to destroy the facilitiy. The result was the entire loss of the Resistance strike force, as well as Jacob Rivers' future self from previous timeline. Only Jacob survived the attack, but with the help of his future self, he was able to obtain the true coordinates of Skynet's Central Core. He later gave these coordinates to John Connor, which led the Resistance to launch an assault on the Skynet facility where the Core and TDE were located, finally ending the war.
- T2 3-D: Battle Across Time (First appearance)
- The Terminator: Dawn of Fate
- Terminator Genisys (Mentioned only)
- Terminator Genisys: Revolution
- Terminator: Resistance
- T2 3-D: Battle Across Time
- Terminator Genisys
- Official Instagram of Terminator Genisys: Future War
- The Final Battle issue 5
- However, due to the advanced complex design and limited self-awareness and Skynet's fear of the T-1000000 becoming independent of its creator, there is no verifiable evidence that the T-1000000 ever came into existence prior to its sending back the Terminators to eliminate John Connor and its destruction at the hands of the Resistance.
- Terminator 3: Rise of the Machines (novel)
- As shown in Terminator Salvation: The Final Battle issue 1