Santorini is essentially what remains after an enormous volcanic eruption that destroyed the earliest settlements on a formerly single island, and created the current geological caldera (a giant central, rectangular lagoon is surrounded by 300 m (980 ft) high, steep cliffs on three sides.) It has been a popular destination in Europe for natural beauties and night life. Capital Fira and one of its big cities Imerovigli and Oia are must-see.