If you drive down Coast Highway 1 from Monterey, you'll see a large, hump-shaped rock nearly separated from the shore. There's a flashing light on this volcanic block, and you need to look closely to notice that a smallish lightstation sits high on the rugged rock's backbone.
I wish I'd gotten a chance to tour this one ... you can call 408-625-4419 for info on guided tours (Sat 10:00 and 2:00; Sun 10:00 plus others, including moonlight tours). Without a tour, you can only gaze from the highway.
If you're in the area, seek out the Nepenthe restaurant. It's up in the hills nearby, and if dining in a giant treehouse overlooking the ocean appeals to you ... well you'll have to see for yourself.