Santorini is a small archipelago of volcanic islands situated in the southern Aegean Sea, about 200 km south-east from Greece mainland. It is the southernmost constituent of the Cyclades group of islands. Santorini is basically what is left of an enormous volcanic explosion, that destroyed the earliest settlements on what was previously a single island, and leading to the creation of the current geological caldera. Its stunning physical beauty, along with a vibrant nightlife, has made Santorini one of Europe's tourist hot spots. The name Santorini comes from the thirteenth century Latin name that is a reference to Saint Irene. Santorini was united with Greece in 1912. Its major settlements include Fira (Phira), Oia, Emporio, Kamari, Imerovigli, Pyrgos, and Therasia, and Akrotiri is a major archaeological site with ruins from the Minoan era. The island's primary industry is tourism, particularly in the summer months.