This is the only surviving Roman lighthouse in Britain and one of only a few in the world. There were originally two of them, one on each of the hills next to Dover harbor. The second one is still visible as a foundation outline in the grass on Dover's second hill. In the daytime, they would have been visible from well out to sea. At night, they had some kind of fire that burned all night. Later this one was converted to a plain watchtower, so the way the fires worked is not completely clear.
The inside is an empty ruin. However, you can see holes in the masonry where beams once supported floors. There doesn't seem to have been a stair, so you probably moved between floors by ladder and trapdoor.
The COG doesn't get excited about Roman stuff. He obviously didn't read Rosemary Sutcliffe at an impressionable age. Or take Latin in school.
Next to the lighthouse, there is the finest and largest surviving Anglo-Saxon building in Kent - namely a church, St. Mary in Castro. I'm pretty excited by Anglo-Saxon stuff, too, but, really, after the Pharos, I hardly noticed it.