Subchamber 1 is where Samus first battles Metroid Prime's Exoskeleton form. Once the creature has been damaged enough, it will create a hole in the ground and fall down to Subchamber 2, where the battle continues. While within this chamber, Metroid Prime will only switch to the colors of the Wave Beam, and the Power Beam, one after another.
- Phazon Infusion Chamber (via one-way entrance)
- Subchamber 2 (via one-way exit via hole in the ground)