Phazon Infusion Chamber

From Wikitroid, the Metroid wiki

The Phazon Infusion Chamber is where Metroid Prime becomes infused with phazon. Samus disturbes it from its slumber and Prime battles her. Metroid Prime breakes a whole in the wall and jumps down it. Samus follows it which leads her to Subchamber 1. Once Samus defeats Metroid Prime in Subchanber 4, it knocks a whole in the wall to its right hand side and falls down it. It leads to Metroid Prime Lair.