Cataniasits under Mount Etna, the most major active volcano in Europe, and has been destroyed many times in the past.
Now a visitor attraction, the Underground Hospital (interior pictured) in Mount Isa was built underground in case of Japanese air raids during WWII.
In Kailua-Kona there are diving excursions to see giant manta rays at night, and its reportedly the best and most reliable place in the world to see them.
