From the exit, head toward the tall rock outcropping to the northeast. Use standing jumps to get up the sand dunes that are too steep to climb.
When you reach the top of the dune near the tall rock outcropping, you'll see the stele with scaffolding where you killed the bad earlier. It will be off to the northwest. Walk around the rock outcropping to the right (south). . .
. . . taking care not to slide down the dunes into the deep pit to the left.
As you round the outcropping, you should be able to see the rock arch where you entered the dunes ahead (to the south). Cross the sand and go through that archway.
Now follow the canyon to the right (west), past a few spike pits, then down a steep hill.
At the base of the hill, the canyon turns left (south) and there's a steep upward slope. Look for an opening in the rock wall on the right. Climb up through the opening, up onto the ledge inside, then up the ladder-like rock wall.
Don't rush out on the other side. There's another pit just beyond the opening. Jump to the side of the pit, then head to the left (west). Vault onto the low step spanning the cave, and continue up and around the corner to the left (south).
Here you'll see the carved entrance to the RAMP WITH SPIKE CLUSTERS. Walk up the left side of the slope until Lara is standing at the base of the slippery part of the slope (arrow with dotted line). From there, take a standing jump to the top of the ramp (arrow with solid line) and land at the top of the slope. On the other side of the opening, follow the long ramp down to the gate, which is now blocked by the spiked balls
