In the film it looks as though it may have been newly completed because of the utter bareness of the thing and the fact that the retaining wall slope is completely free of vegetation. These days you can't even see the thing thanks to natural growth.
Iconic Lion Rock in the background
Once at the reservoir, Page attaches a hook to his climbing rope and proceeds to climb each step on the shaved hillside (each one about 30 ft high) by using his rope as a grapple. Giving it a good heave each time to get it to catch on the lip of the concrete above. All quite impressive.
We get a quick glimpse of the curved road near Lion Rock Tunnel (top picture) before Page hurls himself off the top in a quick taster of what he does later on Lion Rock.