In both games, this is a shaft connecting between the three corridors on the upper right side of Kraid's Lair.
In Metroid, this is a tall shaft composed from grey-white block tiles and black rocks, with green bushes growing out of the walls. Multiple ledges in the walls can be used to ascend and descend the shaft, and it leads into three rooms on the right, all of which exit into another vertical shaft on the right. The room is inhabited by multiple Zeelas and Rippers, and it does not lead anywhere important.
In Zero Mission, the room's appearance is somewhat changed and its role is increased. This is because the normal course of events (without Sequence Breaking) now require Samus to come to this region of Kraid to reactivate the zip lines. The shaft has decreased in height, and each door is now found on ledges protruding from the right wall, leaving a narrow gap next to the right wall for Samus to drop down. Samus enters the room via the uppermost door (from the highest corridor). The right wall initially appears to be solid, with a single blue block in the wall being the only hint that something is hidden.
At the very bottom left of the room is a Morph Ball launcher, which Samus can use to launch herself back to the top of the shaft. Doing so, she can drop down again and lay a Bomb near the block in the wall to expose a hidden tunnel. This leads into a small alcove with a midair block, which four Zeelas are found crawling around. A Red Hatch here leads into the hallway with the machine that reactivates the zip lines in Kraid, allowing Samus to access more of the lair. Another block with the same amount of Zeelas is found directly below the second level of the shaft, to the right of the launcher.
When Samus has defeated the Acid Worm in its room (through the bottom right door of this shaft), she must return to this shaft and launch herself to the top in order to leave the upper-right part of Kraid.
- "Kraid's highest corridor" (via Blue Door)
- "Chozo machine hall" (via Blue Door in Metroid, Red Hatch in Zero Mission)
- "Acid Worm's room" (via Blue Door)
- 8 Zeelas
- 076 LAUNCH UP TO THE RED HATCH (pg. 45)
- "Along the left edge of the lair's upper-right section, you'll fall through a narrow passage. As you do, press B repeatedly to set bombs. If you set a bomb in the right place, a notch will open in the passage. Use the launcher at the bottom of the passage to rocket upward, then roll into the notch as you fall back down. You'll roll close to a red hatch."
- 082 EXIT FROM WHERE YOU ENTERED (pg. 46)
- "After you've explored the lair's upper-right region, launch up the left side then run right and use a ceiling mechanism to slide over the acid on the right side of the long corridor."