The. Rock. Is. A. Secret.
I'm not originally from CT so I don't hold myself to Capetonian rules :)
This is one of the great lookout points in CT; you can see all round sea point, Camps Bay and the 12 Apostles. It's magnificent, drive ALL the way to the end of Ocean View Drive and you'll spot it there.
Sundown is the best time.
363, 405 Ocean View Dr, Bantry Bay, Cape Town, 8005, South Africa