Sail the caldera to a smoking crater and hot springs

The bay you sail across is the inside of a volcano. The eruption that made it, around 1600 BC, was one of the largest in human history, and the island in the middle is still active.

Santorini is what remained after the Minoan eruption emptied the magma chamber and the centre of the island fell into the sea. The cliffs you look up at from the water are the caldera wall, banded in ash and pumice, and the villages sit along the rim of the collapse.

The boat crosses to Nea Kameni, the black cone at the centre, which has emerged from the sea only since the sixteenth century. A twenty-minute climb over loose volcanic rock reaches the crater rim, where the ground is warm and sulphur vents smell exactly as you would expect. Nearby Palea Kameni has iron-rich warm springs you swim into from the boat — they stain light swimwear orange, permanently.

Most itineraries finish with the sail back under the cliffs at sunset, which is the standard Santorini photograph taken from the one angle most visitors never get.