In both games, this is a corridor directly on the left of the lair's entrance shaft, although in the remake a Save Room separates the two. The corridor contains a Missile Tank and leads into the leftmost shaft in Kraid's Lair.
In Metroid, the room is divided into two parts: a square alcove on the right, and a corridor on the left. It is divided by a wall of blue bricks, with two tunnels that Samus can pass through in her Morph Ball. The tunnels have a small number of Bomb Blocks in them. The alcove has little to speak of in terms of features aside from a small pool of acid and an Air Hole that indefinitely spawns Geegas. This provides Samus with an opportunity to refill her energy and Missile Ammo by killing each Geega that comes out. Through the wall is a longer corridor with a larger pool of acid and two more small ones. Above the larger lake is a group of seven midair pillars that are spread out, and a Missile Tank is atop the center. In the middle of the room is a raised section of floor with another Air Hole, and before the exit on the left are a pair of acid pools and two pillars on the ceiling, and one on the floor. A lot of enemies are found here, and the close quarters nature of the room makes it tricky to navigate unless Samus is prepared.
In Zero Mission, the room's appearance has significantly changed, and it is most likely not visited immediately. The secret alcove with the acid pool, five pedestals and the Missile Tank has been moved to the lower right, and can only be accessed from a small tunnel in the Save Room to the left of the central shaft. The left part of the room is much larger and has two levels with one door each, both leading into Kraid's leftmost shaft. The architecture is now a combination of a light and dark purple, whereas in Metroid it was blue. Ruined walls can be seen extending into the background, along with curious fungi or cacti-like plants with red pustules.
Samus can only enter the pit through the lower door, where she is greeted by a Baristute. After defeating it, she can scale a wall and climb up to the top level using ledges. On the top level is a tight tunnel the Morph Ball can fit through, with the bottom made of Fake Blocks. The upper door remains locked until Samus defeats a second Baristute directly under this tunnel, which she can do easily using the Wave Beam (if obtained early) or by dropping below using a Bomb and killing it with her weapons. Once the beast is felled, Samus can leave and access a Missile Tank in the previous shaft.
- Save Room 1 (via Morph Ball tunnel)
- Bottomless Pond (via Blue Doors)
- Missile Tank
- In Metroid, this is found in the left hand side of the corridor.
- In Zero Mission, Samus must enter the room from the tunnel in Save Room 4 to access this tank.
- 011 NO BOUNDARIES (pg. 130)
- "There's no such thing as a dead end to Samus Aran. When you reach the wall on your way to the left side of the hideout, plant Bombs and blast through the barrier one block from the ground. You'll uncover a hidden path to a Missile Tank."
A truncated version of this passage is present in the Zero Mission guide (see below).
- 070 missile tank (pg. 44)
- "Record your progress in the save room to the left of the elevator, then plant a bomb in the lower-left corner and hold Left on the Control Pad. The blast will lift you into a path and you'll roll toward a Missile Tank."
- 085 missile tank (pg. 46)
- "Once you reach the left ledge, climb up, open a hatch and run to the right. Let the large enemy jump over you, and hit it with missiles. After you defeat the beast, climb up and fire diagonally downward into the next area to dispatch another monster. With both enemies gone, you'll have access to a Missile Tank."
- 011 NO BOUNDARIES (pg. 130)
- "When you reach the wall on your way to the Missile Tank on the left side of the hideout, plant bombs and hold Left on the Control Pad to propel yourself through a hidden passage."