As you exit the clearing with the access point, turn left and keep going until you reach a fork. It's actually a crossroads — make a sharp, almost 180° turn right and you'll see another path between the trees.
On top of the rock formation
From the end of the eastern stream, west along the cliff edge is a path that takes you to the top of the rock formations lining the ravine edge.
Down the cliff side & in the ravine
Make your way down the path at the southwest edge of the cliff and you will eventually reach a small hole in the cliff face with a machine standing next to it.
Unlock elevator to City Ruins
Across the ravine
In the clearing at the west corner of the area.