The cell is very minimal. It is a 2x2x2 box with water at the bottom and an end crystal filling the entire cell. The guard can dispense tnt into the cell if the prisoner needs to be killed.
Outside defence
The roof is covered in bubble columns to prevent using a pearl to get on the roof (almost). There are area banned walls all around the center. The large area around the prison is destroyed down to 1 layer of bedrock to prevent hiding a launcher or any sort of machine from the guards.
More security
A lockdown ban test is run to check for invisible players. There is a zone protection item (item frame ban) inside the prison that covers the prisoner, warden area, and much of the visiting tunnel. Before the visitor enters this area, it will be removed for one second, during which time it is difficult for an escapist to enter the area. A guard remains in the end to prevent using end exploits.
