NOTE: It's possible to obtain this secret any time after picking up the third TRIDENT, but to save backtracking, I've included it here, after obtaining all FOUR TRIDENTS but before entering the TEMPLE OF POSEIDON.

After obtaining secret #3 and dropping down into the ROOM WITH CIRCULAR SKYLIGHTS, LOWER LEVEL, WEST ROOM, as shown in the previous section, go through the only doorway leading out of this room into the long aisle between the rooms. Turn left (north)...

...and head for the end of the aisle, jumping over the shallow pit along the way.

When you enter the small room at the north end of the aisle, the door closes and the floor rises ascends.

When it stops, climb into the raised passageway.

Follow it to SECRET #4 (48/70). Shoot the breakable urn to find a large medipack, wideshot shells, and explosive arrows inside (3 separate pickups).

Go up the short ramp to the high doorway.

Safety drop to the ledge below. Move to the right edge...

...near the window into the elevator room.

Safety drop into the long aisle on the LOWER LEVEL.

Hop across the shallow pit and return to the far (south) end of the aisle.

Turn right and and follow the stairs...

...back to the HUGE ROOM WITH HIGH PLATFORM, ROPES, AND SMALL POOL.

If you have all FOUR TRIDENTS, you can now go through the large doorway near the pool to enter the next level, TEMPLE OF POSEIDON. If you're missing one or more TRIDENTS, check this separate page with tips for finding them.

[Catacombs Walkthrough]