- "Fear. A Jedi spends his whole life training against it. But at the Citadel, breaking Jedi is our specialty. Within these walls, they will learn to fear us. And if not, they die."
- ―Osi Sobeck
- "The Citadel wasn't designed to hold common criminals, it was created to hold Jedi if any of us lost our way."
- ―Anakin Skywalker
Built five hundred years before the Clone Wars, the Citadel was originally designed by the Galactic Republic to hold rogue Jedi Knights. During the Clone Wars, it fell under control of the Confederacy of Independent Systems, which conquered Lola Sayu early in the war. It was run by warden Osi Sobeck, who was considered to be sadistic. The Jedi Archives was known to have information on the original layout of the facility, but this was considered extremely old and outdated by the time of the Clone Wars.
Under Separatist control, the Citadel became known as the Confederacy's most isolated holding facility. The prison was heavily guarded by a number of droids including BX-series droid commandos and hundreds of electro-mines. The clone trooper training facilities in Tipoca City on Kamino used a training course simulating an attack on the Citadel as part of their programs. During their trials, Domino Squad succeeded in completing the course.
At one point, Jedi General Even Piell was captured, incarcerated and tortured for information regarding the Nexus Route in the Citadel, prompting an elite rescue team led by Jedi Generals Obi-Wan Kenobi and Anakin Skywalker to free him. After climbing a steep cliff-face dotted with electro-mines, the task force successfully infiltrated the prison and rescued Piell and Tarkin with the help of R2-D2 and a squad of reprogrammed Separatist battle droids. Echo was shot by a droid commando and died on the platform outside the facility. During the Jedi's escape with their clone troopers across Lola Sayu's unstable terrain, a group of anoobas and droids led by Osi Sobeck attacked them. The Phindian Warden was killed by Ahsoka Tano while attempting to throw Captain Tarkin into a lava gorge, and General Piell was fatally injured by one of the anoobas. Piell managed to whisper his Nexus Route information to Ahsoka Tano before succumbing to his injuries, however, and Ahsoka later passed on the crucial intel to the Republic. 
- Star Wars: The Clone Wars – "Clone Cadets" (First mentioned) (Indirect mention only)
- Star Wars: The Clone Wars – "The Citadel" (First appearance)
- Star Wars: The Clone Wars – "Counterattack"
- Star Wars: The Clone Wars – "Citadel Rescue"
- (First identified as Citadel)
- Star Wars Character Encyclopedia (First identified as Citadel Station)
- "Season Four Secrets"—Star Wars Insider 128
- Star Wars: The Clone Wars Comic UK 6.24
- Star Wars: The Clone Wars: The Complete Season Three
- Star Wars: The Ultimate Visual Guide: Updated and Expanded
- Star Wars: The Clone Wars Comic UK 6.41
- "100 and Counting"—Star Wars Insider 139
- Star Wars: The Clone Wars Comic UK 6.51
- Star Wars: The Clone Wars Magazine 20