On the south end of the island is an archaeological site called Akrotiri
This site itself in not open to the public but these are reproducations of some of the paintings found there

These wall paintings are from before the volcanic eruption in 1650 BC and are from the time when Santorini was part of the Minoan civilization

There are other famous wall paintings from Akrotiri but these are my favourites

These paintings demonstrate that this society was a great sea faring nation