In multiplayer, this level is also notable for featuring Duke-Tag, a multiplayer game mode unique to this map.
There are 7 secrets in this level. However, due to symmetrical design of the level (cause by availability of the Duke-Tag game mode), most of them can be grouped together.
Secrets #1-4: Balconies
They are located in the corridors on the sides of the purple lava. There are 2 on the green side and 2 on the brown side - situated on the sides of the door where you enter the are with water. You need a jet pack to reach the balconies - one can be found underwater on the brown side, inside a small aquarium-like room with 2 switches.
When you have the jetpack, simply fly onto each of the balconies to trigger the secrets. The ones on the brown side contain 2 packs of rockets for devastator and 2 boxes of ammo for shotgun and the ones on the green side contain 2 boxes of ammo for chaingun cannon and 2 boxes of rockets for RPG.
Secrets #5-6: Alien pipes
These are also located symmetrically on green and brown sides. They are behind the main gate leading to those 2 areas, but outside of the main structures. You can access them from behind - on the green side, opposite to the place with air tank and on the brown side opposite to the place with protective boots. They are accessed via the organic-looking, alien holes on the walls.
Each of the secrets contains ammo for RPG, chaingun cannon, devastator and shotgun, box of pipebombs. The one on the green side also contains 2 small medkits. Aside from being secrets, they can be useful for fighting the mini battlelords inside the structures, as the other end of the pipes leads inside the structure from a good sniping point.
Secret #7: Gasping for air
This secret can be reached during the boss fight with the Queen. You might have noticed there are a couple of holes in the ceiling of the underwater cave the fight takes place in - 3 of them to be exact.
The secret is located in the hole directly in front of the entrance to the cave. Just swim there and emerge from water when you reach the hole, then climb onto small rock shelf with atomic health, portable medkit and an armor, which all may prove crucial during the fight. Also, all of those holes may be useful for avoiding the Queen's electricity attacks.
Achievements (Megaton Edition Only) Edit
Damn I'm Good: Complete this level on any difficulty to earn this achievement.