The room features two areas: the observation area, and the Blast Furnace itself.
The observation area is in a facility suspended over a pool of lava. In immediate view of the entrance is a window overlooking the Blast Furnace. On the right is a side-room with a Terminal inside of it, but it cannot be accessed from here. To the left of the room is a table with unusable computers, and a drop shaft with a black and yellow lining around it. This leads down a long shaft with a ladder, which was likely used by the BOTTLE SHIP staff, but is unusable by Samus. She can re-ascend the shaft using the Kick Climb.
At the bottom of the shaft is a downward slope leading to another wall, and a hatch into the Blast Furnace, initially shut. This part of the room is illuminated in red light. A Grapple Point is present above the wall, and is used to get into a Morph Ball tunnel near the ceiling. This leads to a Morph Ball launcher, which launches Samus through a tunnel in the walls of the Blast Furnace that eventually emerges into a shaft suspended high above the lava below. As she continues to navigate the shaft, she will become stuck above a total of five Grapple Points, which she can release by detonating a Bomb over them. Continuing through the tunnel eventually leads into the side-room with the Terminal. When this is used, the hatch below that leads into the Blast Furnace opens, and a hatch in the side-room opens so that Samus can leave it.
The Blast Furnace is dome-shaped, and filled to the brim with lava, with two masses of solidified rock serving as platforms. There are noticeable veins of lava running through their tops. Around the room are hatches that open and dump trash coming from the other two sectors at regular intervals. There is a large vent on the ceiling, presumably to ventilate fumes from the burning trash, and multiple parts of the walls have the shape of the letter X.
According to concept art within the game, the furnace's inner diameter is approximately 90 metres, and when full, the ceiling is approximately 40 metres tall. During the boss battle the room's lava level rises, but it decreases after the fight.
Samus comes to this room en route to the Geothermal Power Plant. She navigates through the tunnel network and releases the Grapple Points. The second one falls into the mouth of the Vorash - a creature that tried to eat Samus in the lava cavern earlier - when it leaps from the lava and swallows it. The rest of the Grapple Points float above the lava, and are usable.
Entering the Blast Furnace, Samus is attacked by the Vorash and battles it, using the solidified land masses as ground. As necessary, she can grapple to the other mass when she needs to avoid its attacks. Once Samus has defeated the Vorash, it sinks into the lava as it dies. The lava will decrease, and reveal another hatch. This leads into another sloped corridor and Kick Climb shaft, taking Samus into a second observation area with a door to a Navigation Booth. From here, Samus proceeds into the experimental simulated desert area.
Translations provided by the Metroid Database.
- Art 29 - Sector 03 Enormous Blast Furnace (Lava Fish Boss Battle) Scene
- "This place is an enormous (dome-shaped) blast furnace used to purify the lava inside the area. Cycles the lava used inside the sector, and always maintains its fixed level of viscosity. Also serves a role as a trash processing plant for melting waste coming from other sectors."
- "Samus using the Grapple Beam to land on floating platforms."
- "Must be in Morph Ball mode to pass through tube pipes. While passing through the tubes, the reactor is visible below."
- Art 71 - Pyrosphere - Image of the Large Smelting Furnace
- "Equipment (three pieces) has been placed partway through the passage."
- "When passing through with the Morph Ball, destroy the central axis with bombs to continue. It is then possible to pass using the Grapple Beam on the arms that fell."
- "Inner diameter of furnace is approx. 90m"
- "When full, ceiling height is approx. 40m"
- Page 106
- "Enter the Blast Furnace Observation room, then drop down the open hatch on the left side of the room. The hatch leads to a lower level of the room where you must swing up and into a small vent high along the far wall. Use the ball launcher inside the small vent to launch yourself into the Blast Furnace interior.
- The ball launcher sends you into a series of vents high above the Blast Furnace. Roll along the vents and use bombs to shake the Grapple Beam anchors loose from the bottom of the vent. Once loose, the anchors drop down below and begin to hover in place, creating a path across the lava below.
- After releasing all the Grapple Beam anchors, roll out of the shaft and fall back into the Blast Furnace Observation room with the computer. Use the computer console to open the hatch in the room below you, then back out of the computer room and drop back down the open area on the left side of the room again. Instead of using the anchor in the room like you did last time, now make a left into the open hatch and enter the Blast Furnace room.
- Use the Grapple Beam to swing out into the Blast Furnace. As you do, a massive whale-like creature, Vorash, leaps out of the lava and attempts to swallow you! The creature forces you to let go of the anchor and you fall onto a small floating chunk of rock on the lava.