The tunnel is named as such because it serves as access to an elevator to the Phazon Mines. The room contains a narrow bridge over Phazon that can cause damage to Samus if she falls in it. When she walks near it, a message saying "Intense radiation detected." will appear on her HUD. This is the only time this happens. In the PAL versions of the game, the Power Suit will also say "Radiation detected."