After the prehistoric submergence of the center of ancient Strongyle,
the sea surged into the void which was created and filled it.
In this way the caldera was created which, in some places,
is 400 meters deep. Its walls rise up out of the sea and constitute a unique
section through the earth for study by geologists and vulcanologists.
The wind at the edge of the caldera is usually stronger, so most of
the mills of the island are built there on the caldera. Most of the
villages of Santorini and Therasia are built on the edge of the caldera.