I’m sure my old art teacher would have had a field day analyzing this, and yes, it’s precisely what it looks like:
An ancient lighthouse (and not a penis).
The image would work just fine without it, but it adds some intrigue to the picture.
I shot this with hard sunlight reflected off the water. Other than composition, my main contribution to the excellent posing skill of The Endless Sinner is making sure her arm casts a shadow that adds a bit of mystery to the image.