The grand tree room is one of the largest rooms in the Biosphere. Its name comes from the giant tree in its center, around which is a spiraling walkway leading to a higher area. The room initially opens with a bridge, over which two large vines have extended; these can be vaulted or jumped over. The tree is surrounded by a platform with an impenetrable gate dividing half of it off. From this platform there is a bridge to another door that acts as a later shortcut between this room and the Biological Experiment Floor. This platform is also where the upward walkway is accessed.
The walkway curves around the grand tree, with some of its branches stretching over the path. Multiple species of unnamed plants are including what resemble inactive Gripper-like venus flytraps and two-dimensionally rendered purple-yellow leaves. It ends abruptly near the tree's top, and branches off toward a metallic, circular platform and walkway. The platform resembles a lift and contains a terminal, but it cannot be used as such by Samus. It was likely used by the BOTTLE SHIP's ringleaders to transport cargo.
At the end of the upper walkway is a Fly Pod that infinitely spawns Reos until destroyed, as well as clusters of the same leaves, tree branches, and a unique flower near the door, which is covered in vines. These can be destroyed using a Missile, which will cause them to melt and reveal a door to a Navigation Booth.
When Samus returns to this room in pursuit of a lone soldier, a brief cutscene shows him running through the door to the hallway. Two Mighty Griptians now appear in the room, although Samus is not required to kill them.
- "Fly Pod hallway" (via automatic door)
- Navigation Booth B (via automatic door)
- "Crumbling hallway" (via automatic door)
- 2 Grippers (on walkway, first visit)
- Fly Pod spawning Reos (summit)
- 16 Geemers (12 on lower bridge, 4 on upper bridge)
- 2 Mighty Griptians (lower walkway, after Ridley battle)
- Missile Tank
- Requires the Speed Booster. Samus must speedrun to the top of the spiraling walkway, and Shinespark at its end to reach this tank. She can obtain this when she is pursuing the Deleter, or after the credits.