About 2 km outside of the town center of Sorrento, Italy is a natural pool set behind the bluffs that characterize the Amalfi coast. You can only reach it on foot (or Vespa) by turning right off of Via Capo at the sign on a red building that reads, "Ruderi della villa romana di Pollio." At the very end of the cobblestone street, when you start to hear the rasp of waves on the rocks, you've gone far enough to see the pool and find the ruins above.
Along the cliffs used to sit Pollio Felice's villa, the abode of a Roman noble of centuries ago. The sea below feeds behinds the rocky shore through an arch and makes a circular pool with natural privacy. The water is a shocking cerulean blue, and calm—perfect for a dip. When I was there during a chilly weekend in April, there was no one to be found except two Italian women sitting on the cliffs, chatting in the sun and peeling oranges to eat. If you go when it's warmer, you'll encounter plenty of locals who come to swim. It's a peaceful sojourn outside of Sorrento, and worth it to go swimming if the town's thin beaches are too crowded or closed in the off season.