The volcano of Santorini is considered one of the biggest active, underwater volcanos worldwide.
Its eruption which changed the history and formation of the island occured during the Minoan era about 3.600 years ago. The catastrophe the volcanic eruption caused had a disastrous effect not only on the actual land of Thera, but also on the nearby islands, and generated a tidal wave which reached even the island of Crete.
Nowadays, Santorini's volcano is famous all around the world and hordes of tourists travel to Thera only to have a tour around the volcano. There are boats which offer the volcano tour and usually commence from Fira, at Gialos Port and Ammoudi, under Oia.
You should keep in mind that, especially during the summer, hiking on the volcano is not an easy, relaxing activity. However, the view from the volcano to the Caldera and to its settlements and your overall experience will be totally worth it!