Euphemos, the son of Poseidon and Europa, dreamed of making love with a beautiful nymph, daughter of the sea god Triton. Soon after that she announced him, that she is pregnant, but also afraid to tell it to her father, who would get very angry. As she needed a safe refuge to hide herself and to give birth, the nymph asked Euphemos to grab a lump of earth and to throw it into the sea.

After Euphemos woke up, he could not stop thinking of the beautiful nymph and decided to follow his dream. He took a piece of earth, from the island where the Argonauts have landed and as soon as they continued their journey, he threw it into the wide sea. Suddenly, an island appeared in front of them. The nymph found the necessary shelter here and brought her child into the world. Euphemos called the island Kalliste ("the most beautiful one") and their son got the name Theras, what has later given the island its name "Thera".

Although the story is just a myth, requesting much of imagination, many studies indicate, that the creation of Santorini out of nothing must not be very far from the truth, as the geologists think, that the island was formed after an eruption of a volcano.