Secret 1: Devastating office
The first secret is related to the blue key. At the top of the building next to the bank, you have to flip a switch to reveal a blue key. This switch also opens a compartment behind a painting in the room. Go into the compartment behind where the painting was to collect the devastator and the first secret.
Secret 2: ATM machines
The second secret is the ATM machines in the corner of the exterior bank area. Both of them will open up and lead to a secret room. Go in either of the ATM machines to collect a ripper chaingun and the second secret.
Secret 3: Behind the phone
The third secret is immediately beyond the large locked blue door. There is a pig cop hiding in the darkness to one side of the entrance. Once he's gone, you will see there is a switch up near the ceiling. Once you shoot the switch, the phone that is behind you will move up, revealing a holoduke in a hidden area. Grab the Holoduke for the third secret.
Secret 4: Artistic Jetpack
The fourth secret in this level is in the office with a desk inside the bank. Behind the desk is a painting. Go up to it, and open it. This will reveal a couple of health packs as well as a Jetpack. Go in there to get the items and the fourth secret.
Secret 5: Gamma gear
The fifth secret is in the gear puzzle. When you are making your way through them, you will find yourself at some point in the Gamma room. If the Gamma room is facing the right way, you will see a large red crack in the wall. Blow up this crack, and it will reveal a large hidden area. Go through this area for the final secret in this level, as well as a big shortcut back to the bank vault door.source
Richard "TerminX" Gobeille, who signed a non-disclosure agreement and was given the complete archive of Duke Nukem 3D development files, stated in an April 26, 2021 post on Discord that the alien room inside the bank vault on this level was repurposed from a series of attempts by the level designer, Richard "Levelord" Gray, to create an alien hive map in a similar vein as The Queen.
- The switch on the wall where the lock puzzle is doesn't need to be used at all and generally only makes the puzzle harder if the player attempts to fiddle with it. All they have to do is simply push the three buttons under the desk and ignore the switch on the wall altogether. The switch was most likely put there deliberately to confuse players and make the puzzle more difficult.
- The Battlelord Sentries in the vault may randomly wander outside the map if the explosives detonate before opening the door. (This can be done by throwing a Pipe Bomb through the seams of the door.)