Time Prison is an unseen mentioned in the episode "A Rickle in Time". The Fourth Dimensional Being threatens to imprison Rick, Morty, and Summer for illegally obtaining a Time Crystal. Only knowledge about Time Prison comes from one quote by the Fourth Dimensional Being: "You know what they do to third-dimensional life forms in Time Prison? Same thing they do in every other prison, only forever." Based on that quote, it is presumed, that in Time Prison, time moves differently than in the normal reality so let it's inhabitants live forever.