Twin Fires Tunnel is a room in Magmoor Caverns in Metroid Prime. It consists of a large pool of lava that Samus must cross using the Spider Ball Track accessible at each end of the room. After acquiring the Gravity Suit, traversing this room becomes much easier, as Samus can walk through the lava (while taking damage) and jump towards the ledges to reach any of the two doors.
It is possible for Samus to pass this room without the Spider Ball by a difficult jump to the other side. Alternatively, a Double Bomb Jump out of the lava on the far side of the room is possible at a certain elevated spot.