Santorini is the rim of a drowned volcano. About 3,600 years ago the Bronze Age island of Thera blew itself apart in one of the largest eruptions humans have ever witnessed, and the sea poured in to fill the crater. The crescent you land on today is the surviving wall of that blast — white cliffs rising some 300 metres out of a bay that drops nearly 400 metres straight down, the flooded caldera. Bands of black and red lava stripe the rock, and along the top edge the cube houses of Fira, Imerovigli and Oia trace the crater's lip in a bright white line. Under the ash at Akrotiri lies a Bronze Age town that the eruption preserved almost whole, with paved streets, two-storey houses and three-thousand-year-old wall paintings. It survives so completely that many scholars believe the memory of it became Plato's legend of Atlantis.
Walk the lanes of Oia at the end of the day and you join a slow crowd climbing to the old castle, where the whole caldera turns copper and the blue church domes fall to silhouette over the Aegean. Mornings are the island's quiet hours, best spent over a coffee on a cliff-edge terrace, with the boats far below still moored and motionless on the water. On the flat ground behind the rim, farmers coil their vines into low, ground-level baskets called kouloura to shield the grapes from the wind, then press them into Assyrtiko, a white so sharp and mineral it tastes of the volcano. The volcano is not finished: the black cinder cone of Nea Kameni still smells of sulphur and last stirred in 1950, and the caldera is watched closely. Success has a price, too. So many visitors now come that the island has capped the number of cruise passengers allowed ashore, and at sunset in Oia the crowd is often more striking than the village itself.