Koloumbos is a peaceful beach at the north part of Santorini Island, almost 4 km far from the traditional village of Ia. Although today is a beach ideal for calmness and relaxation, in the bay of Koloumbos is an underwater volcanic crater which was formed in 1650 AD, after a strong volcanic eruption, the biggest one that took place in the Eastern Mediterranean in the last 1000 years. The top of the crater is 18m. under the surface of the sea.