St. Pauli Elbe Tunnel
Zhangjiajie (simplified Chinese: 张家界; traditional Chinese: 張家界; pinyin: Zhāngjiājiè), also known in Tujia language as Zhangx jif avlar (dzaȵ˩ ji˥ a ˩la˥), is a prefecture-level city in the northwestern part of Hunan Province, China.
The Darvaza gas crater (Turkmen: Garagum ýalkymy), also known as the Door to Hell or Gates of Hell, is a natural gas field collapsed into a cavern located in Derweze, Turkmenistan.
Un nouveau record de profondeur dans Le gouffre de Krubera-Voronya en Géorgie. Cette cavité naturelle est la plus profonde du monde. Une expédition int... - Didier Schürch - Google+
The 426 m (1,398 ft) long tunnel was a technical sensation; 24 m (80 ft) beneath the surface, two tubes with 6 m (20 ft) diameter connect central Hamburg with the docks and shipyards on the south side of the river Elbe.