The Fort de Mutzig, also known as Feste Kaiser Wilhelm II, is located near the town of Mutzig, in the Bas-Rhin department of France. It is one of the fortifications built by Germany at the end of the 19th century to defend Strasbourg.
It was the first new fortification built in what was then German territory after the invention of high explosives, which rendered earlier masonry fortifications obsolete.
A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ventilation openings at various points along the length. A pipeline differs significantly from a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in the tunnel. Some tunnels are used as sewers or aqueducts to supply water for consumption or for hydroelectric stations. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.