The cell has water on the floor and all sides regenerate via a cobblestone generator. The visitor sleeps in the prisoner's bed to enter. Guards can enter by pearl glitching from below.
Outside Defence
Around the prison are many layers of lava and water, to try to stop withers. There are 60 perfectly timed elder guardians that give Mining Fatigue 3 every second.
More Security
The warden can call lockdown, which will close many doors and disable guard functions. The visiting tunnels are specifically packed with features to prevent visiting escapes. Doors are made of netherite and are difficult to get through. There is no space to spawn a wither. When the visitor leaves, they exit through a different portal I guess.
