The volcano in Santorini is the main reason of how the island looks like. It is an active volcano and it last erupted in 1956.
Many groups provide tours to the volcano starting at around EUR 18. It takes about 2 hours for complete tour and tour operators take you all the way to active craters.
Compare quotes from upto 3 travel agents for free
€ 40 onwards
€ 9,989 onwards
€ 18 onwards