There are 9 secrets on this level.
Secret 1: Cola Machine
In the area to the left of the magazine shop at the beginning of the level, you will see rows of vending machines. On the left-hand side, there is a row of red and blue "COLA" machines. Activate the last cola machine on the right to reveal a secret Holoduke in the wall.
Secret 2: Lunar Apocalypse Posters
To the left of the mounted Laser Tripbombs on the subway platform, you will see two large posters of Duke Nukem with the words "Lunar Apocalypse" on them. Open these movie posters to reveal a secret compartment behind them.
Secret 3: Cement Column With Night Vision Goggles
On the subway platform where you can see part of Gun Crazy through a chain link fence, go to the side of the platform with the Shadow Warrior graphic. In the very last cement column that is farthest away from the bathroom area, you can open a secret compartment in the side of the column, revealing a set of Night Vision Goggles.
Secret 4: Locker Behind The Lost-And-Found Counter
Go to the lost-and-found counter in the hallway between the magazine shop and the abandoned train station. Crawl through the conveyor belt tunnels behind the lost-and-found counter. In this back office area, open the locker on the right-hand side. This secret is not counted until you retrieve the Armor from inside the locker.
Secret 5: Outside The Battlelord Sentry Stairwell
After providing the blue access card, enter the newly accessible subway platform in front of you. Outside the stairwell containing the red access card and the Battlelord Sentry, jump on top of the trash bin, and open the miniature "Lunar Apocalypse" poster on the wall above you. Behind this poster is a secret compartment.
Secret 6: Inside The Battlelord Sentry Stairwell
Right beside Secret 5 above, there is an unmarked section of wall at the bottom of the stairwell that can be opened to reveal a secret area. The relevant section of wall is inside the stairwell, in the wall opposite of the stairs, and in the left half of the wall.
Secret 7: Inside The Abandoned Train
Climb on top of the abandoned train. Near the back of the train, a panel has been removed from a window on top of the train. Dropping down into this window will reveal a secret area inside the train. (You can escape by retrieving the Jetpack from inside the train.)
Secret 8: Poster Behind The Train
Behind the abandoned train, an earthquake has caused the train tunnel to collapse, revealing hallways on the left and right sides. In the hallway on the left-hand side (the hallway blocked by a fence), there is a "Riot Master" poster on one of the walls. Opening this poster will reveal a secret compartment.
Secret 9: Behind The Bookcase
In the room with the water fountain and bookcases at the very end of the level, climb on top of the bookcase on the right-hand side (if this proves too difficult, then you can use the Jetpack from Secret 7 above). Standing on top of the right-hand bookcase will lower the left-hand bookcase. Behind the lowered bookcase is a secret compartment.
There are 4 babes to rescue on this level.
Babe 1: Hidden Room In The Battlelord Sentry Stairwell
In the hidden room from Secret 6 above, activate the unusual control panel on the far wall of this room. This will open a hidden compartment full of captive babes.
Babe 2: Alongside Babe 1
The second babe is found alongside Babe 1 above.
Babe 3: Alongside Babe 1 And Babe 2
The third babe is found alongside Babe 1 and Babe 2 above.
Babe 4: Island Fountain
After providing the red access card to open the door near the end of the level, you will find two sets of stairs, wrapping around a pool of water in the middle of the room. In the middle of this pool of water, you will see an island bearing a water fountain and a captive babe.
Changes from Duke Nukem 3D
The level begins identically with the revolving doors and magazine shop directly ahead, but there is now a hallway extending to the left, past the vending machines and around a corner.
To the right of the revolving doors and across from the magazine shop (where there was previously just a trash can), there is now a hallway that leads to an abandoned train station, such that the hallway extends in the direction opposite from the magazine shop.
In this short hallway to the abandoned train station, there is a lost-and-found counter and a new secret area in the back office.
In the abandoned train station at the end of the hallway, there is a broken-down train with a secret area inside.
The abandoned train station also contains the platform with Pig Cops and the blue access card panel from the PC version. Behind this platform, the stairwell with the red access card from the PC version can still be found and has not been changed. On higher difficulty settings, however, the Battlelord Sentry at the top of the stairwell is joined by an Alien Beast (Protector Drone) instead of an Assault Commander.
Through an earthquake-induced hole in the wall, the abandoned train station connects with the hallway to the left of the revolving doors at the beginning. This new hallway simply contains some Pig Cops and a janitor's closet.
At the main platform near the start of the level, there is now only one train instead of two, and the train consists of only one train car. Instead of traveling in a loop, the train now travels bi-directionally in a straight line towards the right of the main platform (there is nothing to the left).
The train travels to a new train platform. An inaccessible portion of Gun Crazy can be seen on the other side of a long chain link fence, running the length of the train platform. Behind one of the cement columns, detonating a crack in the wall leads to a parking garage where the blue access card can be found.
The parking garage consists of a single room with several cement columns, a parked truck in the far corner, and the overturned mail truck from Going Postal. The parking garage is initially empty, but several enemies appear once the blue access card is retrieved from atop the parked truck.
Along the train tracks, the hidden weapon compartment from the PC version can still be found, as well as the platform guarded by Enforcers, but the Enforcers are now positioned directly in front of the red access card door, instead of across the tracks from it.
The final room containing the book shelves and water fountain is unchanged.