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Gotthard Base Tunnel, Switzerland -

The Gotthard Base Tunnel is the world's longest and deepest rail tunnel. The 57-km (35-mi) twin-bore tunnel provides a high-speed rail link under the Swiss Alps, linking Erstfeld with Bodio.

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Gotthard Base Tunnel, Switzerland -

Inaugurated on June 1, 2016, the project cost more than US$12 billion (£8.3 billion) and took 17 years to complete. Pictured in July 2014 is the east section of the tunnel at Faido.

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Seikan Tunnel, Japan -

At 53 km (32 mi), the Seikan Tunnel in Japan is the second-longest rail tunnel in the world. The dual-gauge tunnel opened on March 13, 1988, having cost US$7 billion (£5.5 billion). 

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Seikan Tunnel, Japan -

The Seikan Tunnel links Japan's main island of Honshu with the northern neighboring island of Hokkaido. A 23-km (14-mi) section lies under the Tsugaru Strait.

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Channel Tunnel, England-France -

The Channel Tunnel, also known as the Eurotunnel, is a 50-km (31-mi) railway tunnel that connects Folkstone in Kent, England, with Coquelles in France. It is the third-longest tunnel of its kind in the world. It was inaugurated on May 6, 1994 and cost US$6.2 billion (£5 billion).

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Channel Tunnel, England-France -

The Channel Tunnel comprises three separate tunnels—one for northbound and one for southbound traffic—and one service tunnel. It has the longest underwater section of any tunnel in the world. Pictured on December 1, 1990 is the historic breakthrough during construction.

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Staple Bend Tunnel, USA -

The Staple Bend Tunnel in Pennsylvania was the first railway tunnel constructed in the United States. Completed in June 1833, it was the third tunnel of any kind built in the country. It's pictured abandoned in 1911.

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Staple Bend Tunnel, USA -

The 275-m (901-ft) Staple Bend Tunnel still exists, as a US National Historic Landmark. Located at Mineral Point near Johnstown, it's open to the public as part of the Staple Bend Tunnel Trail.

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North River Tunnels, USA -

An excavation team pictured in 1906 pose with the steam shovel used to excavate the North River Tunnels, a pair of railway tunnels beneath the Hudson River. Built between 1904 and 1908 by the Pennsylvania Railroad to allow its trains to reach Manhattan, the lines linked Weehawken in New Jersey with Pennsylvania Station in New York City and are still operational today.

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Bhor Ghat railway tunnels, India -

The rebuilding in 1930 of the Great Indian Peninsula Railway (GIPR) through the Bhor Ghat, a mountain passage located between Palasdari and Khandala, involved the line being moved and new tunnels and tracks being built through the pass. The Bhor Ghat route between Bombay (Mumbai) and Pune runs for approximately 26 km (16 mi) and has about 26 tunnels. The GIPR was opened in 1853 between Bombay and Thane, and was extended through the Bhor Ghat to Deccan in 1861.

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Simplon Rail Tunnel, Switzerland-Italy -

The Simplon Rail Tunnel traversing the Lepontine Alps between Switzerland and Italy consists of two single-track tunnels built nearly 15 years apart. The east tunnel opened in 1906; the west tunnel was inaugurated in 1921. For most of the 20th century this was the longest railway tunnel in the world until the Daishimizu Tunnel in Japan was completed in 1982. The Simplon Rail Tunnel is pictured here in 1956.

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Kilsby Tunnel, England -

The Kilsby Tunnel in Northamptonshire was designed and engineered by Robert Stephenson for the London and Birmingham line. It opened on September 17, 1838 as a single track, and in 1879 a double track was laid. The 180-km (112-mi) long line took 20,000 men nearly five years to build, at a cost of US$6.6 million (£5.5 million). Extensive quicksands made the digging of the tunnel one of the most difficult engineering challenges on the route. Eighteen working shafts were sunk to construct the tunnel, which took two years to complete, cost three times the estimate, and claimed the lives of 26 workers.

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Central Pacific Railroad Summit Tunnel, USA -

A small army of Chinese immigrants working for the Central Pacific Company in the late 1860s blasted their way through California's Sierra Nevada to build 15 tunnels while completing a transcontinental railway that would unite the nation. The most daunting cavern was the Donner Summit Tunnel (pictured), bored through 505 m (1,659 ft) of solid granite.

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Mount Cenis Tunnel, France-Italy -

The Mount Cenis Tunnel, a railway tunnel from Modane, France, to Bardonècchia, Italy, was the first great Alpine tunnel to be completed. It opened in 1871, running under the Fréjus Pass. It was the first long-distance rock tunnel driven from two headings with no intervening shafts, an incredible feat of engineering at the time and achieved using the then-new technology of a pneumatic drill (pictured).

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St. Paul Pass Tunnel, USA -

Opened in 1908, the St. Paul Pass Tunnel went through the Bitterroot Range of the Rocky Mountains on the Montana-Idaho border. One of the so-called Milwaukee Road tunnels set along its Pacific Coast Extension, the St. Paul Pass, nearly 1.6 km (1 mi) in elevation and roughly the same in length, ceased to be used in 1980. Today it serves as a rail trail route for hikers and bicyclists, the Route of the Hiawatha Trail.

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Congo-Ocean railway tunnels, Africa -

The Congo-Ocean railway links the Atlantic port of Pointe-Noire (now in the Republic of Congo) with Brazzaville, a distance of 502 km  (312 mi). Thousands died during forced labor, the construction workers dying from a combination of both industrial accidents and diseases, including malaria. On the same line many years later, the 4.6-km (2.8 mi) Bamba Tunnel was built. Completed in 1985, this engineering project also claimed the lives of many.

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Moffat Tunnel, USA -

Named after Colorado industrialist and railroad pioneer David Moffat (1839–1911), the Moffat Tunnel cuts through the Continental Divide in the north-central region of the state. Opened in 1928, it also serves as a water tunnel, delivering a portion of Denver's water supply. The tunnel is pictured in 1978, a year before it was was designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.

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Cascade Tunnel, USA -

The Cascade Tunnel in Washington state originally opened as a single-track line in 1900 but was abandoned in 1929 in favor of a new and longer tunnel. Both were constructed by the Great Northern Railway and both went through the Stevens Pass. The existing tunnel is 12.5-m (7.8-mi) long and lies 359 m (1,180 ft) below the pass summit.

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Hoosac Tunnel, USA -

Work began on the Hoosac Tunnel in Massachusetts in 1851 to pass through the Hoosac Mountain range and connect the town of Florida with the city of North Adams. After its completion in 1875, Hoosac was the world's second-longest tunnel after the Mont Cenis Tunnel through the French Alps. It's still active today.

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Seven Tunnel, England -

Pictured: a locomotive exits from the eastern end of the Severn Tunnel in 1930. Opened in December 1886, the Seven Tunnel links South Gloucestershire in the west of England to Monmouthshire in south Wales under the estuary of the River Severn. Once the longest underwater tunnel in the world until 1987 and, for more than 100 years, the longest mainline railway tunnel within the United Kingdom, the Seven Tunnel remains one of the great engineering feats of the Victorian era.

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Summit Tunnel, England -

Constructed between 1838 and 1841 by the Manchester and Leeds Railway, Summit Tunnel in England is one of the world's oldest railway tunnels. It was bored beneath the Pennine Hills to provide a direct line between Leeds and Manchester and was once the longest rail tunnel on the planet. It has remained in continuous use since 1841.

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San Fernando Tunnel, USA -

The Southern Pacific Railroad (today known as the Union Pacific Railroad) still uses the San Fernando Tunnel in Los Angeles, seen here being built in 1880. Over 1,500 mostly Chinese laborers took part in its construction. The first train passed through the tunnel on August 12, 1876. The tunnel is part of the Newall Pass, a major regional transport hub.

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Connaught Tunnel, Canada -

The Connaught Tunnel in southeastern British Columbia carries the Canadian Pacific Railway main line under Mount Macdonald in the Selkirk Mountains. Opened in 1916, the Connaught Tunnel is one of two tunnels set under Rogers Pass, the other being the Mount Macdonald Tunnel.

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Johnson's Canyon Tunnel, USA -

Johnson's Canyon Tunnel in Arizona was completed in 1882 as part of the Santa Fe Railway line. A whole town sprung up during its construction, buildings that included three saloons, two hardware stores, and several bordellos. During the Second World War the railroad line carried troops and military freight through the tunnel. The line was abandoned in 1959 and the tunnel today serves as part of a hiking route. The tunnel and its iron bridge are seen here under construction in 1870.

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Zugspitz Tunnel, Germany -

Pictured: railroad workers in 1929 boring the tunnel through the Zugspitz, at 2,962 m (9,718 ft) the highest mountain in Germany. They were advancing the line from Garmisch to the Zugspitzplatt, approximately 300 m (984 ft) below Zugspitze. The Bavarian Zugspitze Railway is one of four rack railways still working in Germany, along with the Wendelstein Railway, the Drachenfels Railway, and the Stuttgart Rack Railway.

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Landwasser Tunnel, Switzerland -

One of Europe's most scenic rail tunnels, the 216-m (708 ft) Landwasser Tunnel is approached from the southeast by the landmark Landwasser Viaduct. The tunnel's entrance is positioned on a vertical rock wall, having been purposefully aligned with the viaduct. It carries the Rhaetian Railway.

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Spiral Tunnels, Canada -

The Spiral Tunnels were built in 1909 as a means of overcoming the "Big Hill" on the Canadian Pacific main line in British Columbia. The most difficult piece of railway track on the route due to its steep elevation, the Big Hill posed a dangerous challenge to passenger and rolling stock. The two Spiral Tunnels lessened the gradient by effectively lengthening the track.

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Tunnel No 4, Inner Mongolia -

The remote Jing Peng pass provides a dramatic backdrop to a double-headed coal locomotive emerging from tunnel No 4 to traverse the mountainous section of the Ji-Tong railway across Inner Mongolia. The coal train is one of the last stream-driven operations in the world.

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Chiltern Tunnel, England -

The Chiltern Tunnel will carry the High Speed 2 (HS2) railway line under the Chiltern Hills in England. The twin-bore tunnels, which are 16 km (10 mi) long, will be the longest on the HS2 line. The first phase of the HS2 is scheduled to be completed by 2033.  

Sources: (BBC) (Britannica) (Smithsonian Magazine)

See also: The most beautiful train journeys in the UK

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