Santorini

The curve of Santorini is the rim of a crater. Its centre blew out roughly 3,600 years ago and the Aegean rushed in to fill what was left. The eruption was one of the largest in human history. It buried the Bronze Age town of Akrotiri under metres of ash, sent waves across to Crete, and may be the seed of Plato's story about a civilisation swallowed by the sea. What survived is a broken ring: Thira along the eastern arc, Thirasia opposite, and about 400 metres of water between them where a mountain used to stand. The small islands at the centre are younger than the hole they sit in. Nea Kameni and Palea Kameni have been building up off the caldera floor for the last two thousand years, and the newer of the two last erupted in 1950. The blue on this board is not a bay. It is a crater with the sea in it.