This is an underwater shaft that serves as the entrance to Maridia. A very large glass tube runs across the width of the room, providing a dry path between two regions of Brinstar: the "red soil" area, and the rebuilt hideout where Kraid resides. Four mirdair rock platforms exist along the shaft, which is the primary method of climbing it, next to protruding rock ledges in the walls. Tiny plants with blue stems and yellow flowers can be seen growing on the rocks. There are no enemies in the Glass Tunnel.
Samus visits this room early on in the game while she is on her way to Kraid's domain. Once she has obtained the Power Bombs and Gravity Suit, Samus can return to the Tunnel and lay a Power Bomb to destroy the glass tube. When impacted, the glass begins to crack before shattering, with shards of glass raining down to the floor before disappearing. Once this is done, Samus is able to explore Maridia proper. A door below the tube's location leads into a Save Room, while the main shaft of Maridia is through a door in the ceiling.
The tube does not break until Samus moves, jumps or selects an item in her HUD. Similarly, if she detonates a Power Bomb and then leaves the room (perhaps accidentally) before the tube's exploding animation begins, it will not break. She must return and lay another Power Bomb, then avoid exiting the room until the tube shatters.
Despite being part of Maridia, the Lower Brinstar theme continues to play in this room.
- "Brinstar-Maridia passage West" (via opening)
- "Brinstar-Maridia passage East" (via opening)
- "Save Station 1 (via Red Hatch)
- "Maridia Main Shaft" (via Blue Door)
- MARIDIA AREA C (pg. 98)
- "The lower portion of Area C dips down to connect two parts of Brinstar, so you'll use this route as you explore that region. You won't be able to explore this part of Maridia, though, until you find the Power Bomb that opens it up."
- A. CRACK THE CASE (pg. 98)
- "You'll travel through the glass tube that connects two parts of Brinstar often. When you've found both the Gravity Suit and the Power Bomb, you can blow the tube up and begin exploring the mysterious underwater region that you've previously only seen through the glass."