England, West Midlands, Kinver Edge. Carved graffiti in the sandstone walls of the caves in Nannys Rock.

England, West Midlands, Kinver Edge. Carved graffiti in the sandstone walls of the caves in Nannys Rock.

England, West Midlands, Kinver Edge. Carved graffiti in the sandstone walls of the caves in Nannys Rock.

New Zealand, Southland, The Catlins. Tourist admiring the Cathedral caves.

New Zealand, Southland, The Catlins. Abstract view of tourists exploring the Cathedral caves.

New Zealand, Southland, The Catlins. Tourists admiring the Cathedral caves.

Morocco, Central Morocco, The Ouzoud Gorge. The hills of the gorges of Oued el-Abid, photographed from near the caves

Morocco, Central Morocco, The Ouzoud Gorge. The hills of the gorges of Oued el-Abid, photographed from near the caves

Morocco, Central Morocco, The Ouzoud Gorge. The interior of natural caves, popular with tourists visiting the cascades.

Morocco, Central Morocco, The Ouzoud Gorge. The interior of natural caves, popular with tourists visiting the cascades.