Opening the world, you spawn in a flat land and no structure in sight besides some villages and the grotesquely massive prison in front of you. To enter the prison, you must go to the lobby by pressing the button inside the small building with a portal inside. 

After you are sent inside the prison, you see yourself inside the receptionist lobby of the warden. There are levers and buttons on the wall that lead and control different functions of the rooms here like the lockers and the isolation room to cleanse the visitor. 

Going through the next phase, you respawn on an open space leading through the vault. You cross the gap by activating the bridge and afterwards be able to open/close both the vault door and the cell floor. The staircase above the vault is used by the guards for security and maintenance. 

Unlocking the vault door, you see the primary cells used for keeping problematic people in check. Closing the door behind you would be optimal so if an escape attempt is made, this is as far as they go. Walking through the hallway, you go to the courtyard and water passage to be cleansed one last time and swim through the next level. 

Swimming throughout the passageway, you get closer and closer to the main Cell. There are multiple controls for the guard to use to get you through the next phase, they also have their own bunker and storage room for replacing the taken books used for wavers and contracts. There are three floors to the bunker which all have beds for guards to respawn in. 

Walking up the vast amount of stairs, you go to the final phase of getting to visit the main cell prisoner. There are controls to activate and deactivate the lava fall, the barrier and the bridge to take the visitor to the prisoner. Once they're done with conversations the guard will send you back via harming potions that will respawn you in the nearby bed. 

Now then, going back, this isn't all there is to the prison. To enter the guard's rooms and secret entrances, go back to the staircase above the vault door. There are multiple hallways which lead to different areas like storage, ender pearl stasis chambers, security maintenance. 

Be careful not to get lost, there are a variety of hallways that could lead to a few elevators, a maintenance balcony, the main Cell respawning bed, and even a way in and out above the prison used by guards. 

The prison is insanely secure if you want to escape it, most have tried. If you think the watch towers outside are the only surveillance the guards have that is incorrect. They can have surveillance balconies above ceilings, through walls and even beneath the floor that can see through everything. And most importantly the mining fatigue effect which is given to every player in the vicinity of the prison by elder guardians inside the walls. 

Here is a short preview of the features inside the prison. The map is brought to you by colleagues, Creavite and Blaze Escape. The Java edition map links are in their channel. Of course all credit belongs to where it's due, the original creator of Pandora's Vault in the DreamSMP, 'Awesamdude'. This is merely a recreation. 

Here is also a video with the full recreational map of the DreamSMP (the prison here may not be working as well as this) 

UPDATE

New Keycard System: For now only the lockers have this system implemented, there are separate copies of keycards for each locker, you throw one on the slab at the corner of the room and wait until you receive it back from the dispenser, then a button will appear for you to unlock your locker chest and lock it again. 

The bridge in the lava hallway has been updated into a flying machine that goes back and forth. If it freezes midair, simply update the observer block with a flint and steel. The dispensing system has also been fixed to properly dispense the correct splash potion like fire resistance or harming.