Apple tree tunnel Heale House and gardens, Middle Woodford, Salisbury, Wiltshire, England, UK

The town of Orchisar, showing the old tunneled houses dug into the volcanic rock, Cappadocia, Anatolia, Turkey, Asia Minor, Eurasia

The Fouguo, an ancient underground tunnel found, Carn Euny, a well preserved Iron Age settlement, near Sancreed, Cornwall, England, United Kingdom, Europe

Man Caring For Plants in Greenhouse

Entrance of the tunnel Tunnel de Tarragnoz on the Doubs-Rhine-Rhone-channel at Besancon, Doubs, Region Franche-Comte, France, Europe

Beihei Tunnel, the former military tunnel designed to house equipment and personel is now used as a tourist attraction with free boat rentals to tour the caves

Signs on the trekking trail next to the waterfall in Levada do Caldeirao Verde, Queimadas, Madeira

Areaway of the Jin Mao Tower in Pudong, Shanghai, China

A haunted house on a annual fair - Baden Wuerttemberg Germany Europe.

Aerial view, mine Graf Bismarck 3, 5, A2 motorway cover, Schachtzeichen RUHR.2010 art installation, Gelsenkirchen, Ruhrgebiet region, North Rhine-Westphalia, Germany, Europe

Aerial view, mine Graf Bismarck 3.5, Gelsenkirchen, Ruhrgebiet region, North Rhine-Westphalia, Germany, Europe

Entrance tunnel to the interior of the Berber granary Qasr al-Haj, Nafusa Mountains, Libya, Africa

Business center The Squaire, formerly Airrail Center, Terminal 1 of Frankfurt Airport, Frankfurt am Main, Hesse, Germany, Europe

Archway of a tunnel, Pont Yssoir, Sarthe River, Le Mans, Sarthe, France

Tunnels And Caves In The Kaymakli Underground City, Kaymakli, Turkey

Tunnels And Caves In The Kaymakli Underground City, Kaymakli, Turkey