There are 12 cells, containing various decorations. Prisoners respawn via a squilly bed glitch with a shulker; visitors enter through a hole. Mining out is prevented I think by an auto kicker and elder guardians.
More Security
The prison is surrounded by a giant amount of lava pretending to be wither walls. Below is a tripwire pearl glitch detector. Above is a pressure plate roof detector. Since everything, including the pearl glitch detector, is above the former location of the bedrock roof after terra removed 100k+ bedrock blocks, a trap portal is not necessary. There is an item check during entry and all respawn anchors have exactly 1 glowstone in them to prevent the end exploit.
