Santorini isn't just about watching the cruise ships dock and winding your way around the souvenir shops in Fira. You can take a tour out to the island in the centre of the caldera, Nea Kameni by boat. It's here where you realise that living on Santorini has been a pretty precarious existence. The islands are basically sitting on top of a volanco, and it's on the centre island where you can see the suplhur fumes escape from a landscape that doesn't seem to have any vegetation. Another short boat stop away are the hot springs, but when mixed with the cool Agean Sea they were tepid at best!
While you're in the mood for learning about Santorini, check out the museum of Prehistoric Thera in Santorini. It shows how the island's ancient inhabitants lived all those thousands of years ago before volanic earthquakes made it a harder place to live!