It is difficult to enter - one must commit a cosmic crime - and nearly impossible to escape due to the strange, spacial physics of the dimension. It is also one of the most accessed universes. The realm of the Citadel exists outside the conventional fields of space, similar to Prismo's realm. The prison is composed of six massive crystal pillars, focused toward a crystal frame. Each pillar has its own gravitational field, but is held in place by the gravity of the realm's absolute center. The pillars also appear to be in unison with the sentient guardians, and systems similar to the Guradians' bodies can be seen inside. As of the episode "Escape from the Citadel," the Citadel is unpopulated and in ruins. Much of the prison's surfaces have melted and the remaining liquid gravitated to the c