As you might know, there are several (active) volcano's in Iceland. You will see cooled down lava all over the place, but at this show they recreate a volcanic eruption by superheating real lava and pouring it into a showroom full of people.

This is the only show in the world that does that! There's two location in Iceland to see this show (Reykjavík and Vík), so you can choose which would work best in your schedule.

This is the perfect activity for a rainy day.