In both appearances, Corridor No. 3 consists of green blocks and metallic structures. With the higher graphical detail in Zero Mission, the green blocks appear artificial compared to the natural blue rocks of Brinstar. There are several long horizontal silver tubes infested with Zoomers, which Samus Aran must carefully navigate in Morph Ball mode.
In Zero Mission, some of the metallic structures can be activated by firing a beam weapon at the red band, causing the object to adjust its height and let Samus pass through underneath. Corridor No. 3 is also home to unidentified mushroom-like flora, as well as Tangle Vine Fruits that can only be destroyed with parasites.
Corridor No. 3's most significant feature is a small room located about midway through the corridor. Samus can shoot straight up to break through the ceiling, leading to a hidden room above Corridor No. 3 that contains the Varia Suit. The High Jump Boots are normally required to reach the Varia Suit, though Samus can prematurely acquire the Varia Suit by Bomb Jumping or freezing an enemy with the Ice Beam to use as a platform.
- Missile Tank
- In both games, a single Missile Tank can be found resting on a structure suspended above acid, located in the final room.
- Energy Tank
- In Metroid, an Energy Tank can be found in the third room, guarded by a Reo and a pair of Zoomers. This was removed from the room in Zero Mission.
- In Victory Techniques for Metroid, Samus visits Corridor No. 3 during her initial exploration of Brinstar, collecting the Missile Tank and Energy Tank found in this location. After acquiring the High Jump Boots in Norfair, she backtracks to Corridor No. 3 to collect the Varia Suit.