From the THOR SWITCH, take a running jump across the gap to land on the gray pressure pad.
The secret door opens way down below in the southwest corner. Position Lara on the pressure pad facing south (i.e., wall on her right, ATLAS SWITCH on her left) with her feet on the back edge of the pad, as shown here. Until she steps off the pad, the 17-second timer won't start. So take all the time you want to get her into position. Make sure your health bar is at least two-thirds full, since Lara will lose some in the process, and save the game.
Now comes the speed run: Hold Action and take two hops back to drop and hang from the edge. (Hanging for a split second means less damage when Lara falls.)
Immediately let go and drop to the ledge below. As Lara falls, press and hold Roll...
...so that when she hits the ledge, she rolls and comes up facing in the opposite direction. Release Roll...
...and run forward off the edge.
As Lara falls, again hold the Roll button so she lands and comes up facing the other way.
Release Roll and run forward along the long ledge. If you want to, you can draw pistols and kill the 2 bats (13-14) that swoop in from the left, but you must keep moving. If shooting distracts you, don't worry about it. You can get the bats later. Just keep running...
...off the edge.
Lara will take a little bit of damage when she lands, but if you started with full health, she'll still have almost half left. Hold Forward, and as soon as she stands up from the landing animation...
...run straight on through the timed door.
Inside is SECRET #4, a large medi pack (7) and magnum clips (8).
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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