There's very little left of this 6th-century temple. Once it was a magnificent building giving sanctuary to fugitives and wrecked sailors, but in the 18th century it was mostly dismantled and the materials used to build a monastery on Hydra. Still, the walk or drive to the site gives superb views of the Saronic Gulf and the Peloponnese.
With your own wheels, from the road near Moni Zoödohou Pigis, head inland to reach the ruins. Then you can continue along the road and circle back to the bridge onto Sferia. It’s about 6km in total.