Santorini is a 12-mile crescent of land, all that remains of a substantial island blown apart by a cataclysmic eruption more than 3,500 years ago. (The blast probably gave rise to the enduring legend of Atlantis.) Today, stupendous cliffs rise from the sea-filled caldera to blinding whitewashed villages perched more than 1,000 feet above. The island itself is arid, with dark volcanic soil (which helps produce delicious dry white wines) and black-sand beaches. Aside from archaeological excavations, its principal attraction is the unforgettable view, both of the immense caldera and the surrounding islands of the Cyclades. Extremely crowded in summer, Santorini is best visited in spring and fall.