Primal Basilica

The Primal Basilica on Cybertron serves as a place where the bodies of Matrix of Leadership holders are interned. The site is heavily guarded, as a fleet of Sky Spies provide security surveillance, and gluometric particles coat the air, scrambling onboard guidance systems and causing any ships to crash in a 25-mile radius. In addition, the Basilica's perimeter is guarded by the elite Triorian Guard.

IDW Generation 1 continuity
Prior to the Great War, Nominus Prime was buried at the Primal Basilica, but the Matrix within his body was replaced with an explosive device. After learning of this, Orion Pax assembled a team of specialists consisting of Glitch, Windcharger, and Skids to perform the secret mission of retrieving the booby-trapped Matrix and replacing it with another fake.

After Sentinel Prime perished, he was given a public burial at the Basilica but owing to the political climate at the time, the public was not allowed inside. Unknown to all at the time, "Sentinel Prime" was merely a fabrication created by the Titan Master Infinitus who detached himself from his Transtector body and fled to Kaon to commence construction on a replacement. Unable to explain this, the security forces assumed the Decepticons had broken into the Basilica and stolen Sentinel's head.

Prime Wars Trilogy cartoons
The Primal Basilica acted as sort of a spiritual hub, in which the Transformers could pray to, or potentially even confer with, the past Primes. The Chorus of the Primes resided within the Basilica, offering counsel to the Matrix-bearers who sought their wisdom.

Following the Combiner Wars, Stormclash took Rodimus Prime to the Basilica, where he surrendered the Matrix to the Chorus's custody, choosing instead to return to being Hod Rod. The Mistress of Flame was praying in the Basilica when Trypticon was reborn, and Windblade and Perceptor rendezvoused with her there to determine their next course of action. After ordering Perceptor to restore the Basilica's defenses and sending the Combiners to locate Fortress Maximus, the Mistress retreated to the Basilica's Prayer Chamber to pray to the Thirteen for a miracle to save them. Unfortunately, Overlord also appeared in the prayer chamber, and severely beat the Mistress before finally killing her and departing. Megatron later arrived at the Basilica seeking the Mistress's guidance, only to find her battered corpse, so he departed once again in search of Victorion. Perceptor returned to the Prayer Chamber after rebooting the defenses, but upon finding the Mistress's body, he was led away by the recently-arrived Optimus Prime, who activated the Basilica's defenses and fired a massive beam from the top spire at Trypticon. This stalled the Titan long enough for the two to enter the Chorus Chamber and reclaim the Matrix. Prime then led Perceptor through a secret passage deep beneath the Basilica and to a hidden exit, ordering the scientist to get the Matrix as far away from Trypticon as possible. Optimus left the Basilica soon after, receiving a final word of warning from the Chorus as he departed. Ultimately, Perceptor only made it a short distance from the Basilica before the Matrix spoke to him, instructing him to return to the battle and follow its plan to defeat Trypticon.

Optimus Prime and Optimal Optimus were later seen at the Basilica, working to prepare Optimal for his new role as leader of Cybertron. Unbeknownst to them, they were being watched by the ghost of Starscream.