Yes, Sounion. A beautiful temple in a gorgeous setting by the sea. Not much else there, but there are beaches and tavernas on the way.
If you are still allowed in the ruins, you can see Lord Byron's graffiti carved on a column. It is also the place where Aegeus jumped into the sea which was named after him.
The last time we were there we were actually staying at the airport Sofitel. We had arrived in the afternoon and had a very early morning flight to the islands. We had George's pick us up, go to Sounion, had dinner by the beach, watched the sunset and back to the hotel.