Polignano Caves (boat tour)
The sea caves under the cliff are invisible from land: they open at water level and can only be entered by boat or by swimming. Trips leave from the little harbour and are cancelled in rough seas, because the cave mouths close up: plan them with a day's margin rather than on the last day of the trip. It is the only way to understand how the town is built from underneath, and it is the exact reverse of the view from the bridge.

