Underground pictures
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Tourists visit the Kuha Karuhas pavilion located inside the Phraya Nakhon cave, in the Khao Sam Roi Yot national park, some 300 km south of Bangkok, Thailand. The pavillon was built in 1890 on the occasion of a visit to the cave by King Chulalongkorn, the grand-father of current King Bhumibol Adulyadej.
A visitor stands in the Erstfeld-Amsteg section of the NEAT Gotthard Base Tunnel, Switzerland. With a length of 57 km (35 miles) crossing the Alps, the world's longest train tunnel should become operational at the end of 2017.
Mine under Budapest, Hungary.
Carlsbad Caverns National Park near Carlsbad, New Mexico U.S.
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Tourists visit the Kuha Karuhas pavilion located inside the Phraya Nakhon cave, in the Khao Sam Roi Yot national park, some 300 km south of Bangkok, Thailand. The pavillon was built in 1890 on the occasion of a visit to the cave by King Chulalongkorn, the grand-father of current King Bhumibol Adulyadej.
A visitor stands in the Erstfeld-Amsteg section of the NEAT Gotthard Base Tunnel, Switzerland. With a length of 57 km (35 miles) crossing the Alps, the world's longest train tunnel should become operational at the end of 2017.
Mine under Budapest, Hungary.
Carlsbad Caverns National Park near Carlsbad, New Mexico U.S.