Back in the LARGE ROOM WITH THE PYRAMID & SEE-THROUGH FLOOR, head for the octagonal opening on the right (east) wall. It should be open if you used the correct switch earlier in the BI-LEVEL ROOM WITH SIX SWITCHES.
NOTE: You may notice a centaur (31 in the main walkthrough) running around in the room beneath the floor, assuming you also triggered it in the ROOM WITH SIX SWITCHES. It can't reach Lara yet.
Get a lock on the mutant (16) guarding the path beyond the octagonal doorway and back away shooting.
When it explodes, continue to the top.
Vault up onto the low step.
Turn around and pull up onto the ledge above. (It looks like the red-hot stone should burn Lara's hands, but she's far too cool for that.)
Lava begins to flow along the passageway toward Lara, but it stops before it reaches her. She will take damage from the flecks of bubbling lava, though, so don't linger too long.
Turn around again and take a standing jump over the hole where you just climbed up, then another standing jump over a small lava pit to land on a flat spot near the wall.
Turn around once more to face back the way you came. Here there are two black stone ramps sloping upward on either side of the opening where you just climbed up. Go up the ramp on the left.
When you reach the top, use the shotgun to kill the mutant (17) lurking down below on the right before it bombards Lara with fireballs or darts. I haven't found a completely safe spot, but if you stand at the top of the left ramp, you can use the dark stone column between the ramps for cover if necessary.
Climb down the tan blocks. The lava stream continues here between these tan ledges. Pick up the small medi pack (28) on this side of the stream and shotgun shells (29) on the other.
Then jump back across the lava and climb up to the second highest block.
From there, take a carefully angled running jump past the dark stone column into the doorway above the tan slope.
- OR -
Alternatively, climb all the way up the tan blocks to get back to the black ramps.
Jump across the lava and move to the top of the ramp on the right (i.e., right when facing uphill).
Walk forward to the edge, so Lara is standing just above the tan slope, and jump into the doorway below on the right.
DARK MODE: Even with brightness adjusted, dark images on a light background can be hard to see. May I suggest a reputable dark mode browser extension, such as Dark Reader? (Download only from trusted sites, like darkreader.org or your browser's web store.)
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