What Is The Caldera Of Santorini? Santorini, along with Mykonos, is probably the most famous Greek island. Its sun-bleached, smooth-edged houses, azure-domed churches, narrow streets and glorious views over the expanse of the Aegean Sea are emblematic of this little paradise. But not many people know that the volcanic island we know was centuries – or even millennia – in the making. What’s more, few know exactly where its caldera is. To understand this, a little overview of the island’s history is necessary. The group of islands known as Santorini, so named after the small chapel of Agia Irini (or Saint Irene) by the Venetians, is located at the heart of the Aegean Sea and comprises five distinct islands: Santorini (aka Thira), the main island; Thirasia and Aspronisi at the periphery; and the two Kameni islands at the center.