© Istockphoto|Grotta Hang En, Vietnam 

© Istockphoto| Fly Geiser, Nevada

© Istockphoto|Parco Nazionale di Redwood, California 

© Istockphoto|Lago Baikal, Russia 

© Istockphoto|Salar de Uyuni, Bolivia 

© Istockphoto|La caverna di Baatara, Libano 

© Istockphoto| Stromboli