The Sanctuary of Artemis Orthia, on the eastern edge of the ancient city near the modern road bridge over the Eurotas, was one of the most important religious sites of Spartan life. What survives today is the rectangular foundation of the temple and the curved tiers of stone seating around it — Roman additions, built when the sanctuary's notorious flogging ritual had become a tourist attraction drawing visitors from across the Empire.
The site is unfenced, free to enter, and almost always empty. Five minutes' walk from the centre of Sparta. Combine with the acropolis on the same morning.