© Istockphoto|Petra, Giordania

© Istockphoto|Uchisar, Cappadocia

© Istockphoto|Kandovan, Iran 

© Istockphoto|Vardzia, Georgia   

© Istockphoto|Ajanta, India

© Istockphoto|Richat Structure, Mauritania

© Istockphoto|Cliff Palace, Colorado

© Istockphoto| Calcata, Viterbo

© Istockphoto| Setenil de las Bodegas, Cadice, Spagna

© Istockphoto| Guermassa, Tunisia