Directly from the port of Thira you can take part in a popular excursion to the island of Santorini, which is one end of a sunken volcanic caldera, which also includes other small islands. Therasia, Aspronisi, Kameni, Nea Kameni and Palea Kameni are the other emerged lands that are part of the ancient caldera. A nice boat trip will take you to visit them and admire them in a much more specific way.