Stand in the doorway overlooking the slope and the spike pit below. Angle Lara to the right and jump forward to land on the right side of the slope.

Then just slide down...

...to land in the one safe spot at the far right corner of the spike pit.

Pick up the UZIS (or Uzi ammo if you already have the weapons), the only SECRET (66/70) in this level.

Climb out of the pit onto the triangular ledge just above the safe spot.

Step off the edge and as you slide down toward the small, square opening at the bottom of the cave...

...jump forward to land on the opposite slope. Slide back and grab the edge of the opening.

Then let go to drop into the passageway below without taking any damage.

You're now back in the area where you began the level UNDERNEATH THE SPHINX. At the bottom of the hill is the HALL WITH BULL GUARDIANS AND HIEROGLYPH BUTTONS (the gate is still closed).

Head for the top of the slope to re-enter the SPHINX COMPLEX level.

Climb out of the pit between the sphinx's paws.

Go to the right (west) around the corner, which is the right paw of the SPHINX, toward the excavation pit.

Take a running jump along the left (south) side of the pit to land near the stone pillars supporting the metal gate.

Use the GUARD'S KEYS (which you should still have from the MENKAURE'S PYRAMID level) to unlock the doors.

Go through the dark opening to finish the level.

[Menkaure's Pyramid Walkthrough]