The incredible tunnels pushing deep below the surface

By Joe Minihane, CNN

(CNN) — Underneath oceans, burrowed inside glaciers or dug deep into the Earth, tunnels have long been an enduring source of fascination for travelers. Whether speeding passage between major cities, hopping between islands or even acting as a final resting place, these are the world’s most amazing tunnels.

Head torches at the ready!

Gotthard Base Tunnel, Switzerland

At 57 kilometers (35.5 miles), the Gotthard Base Tunnel is the longest and deepest railway tunnel in the world.

Not to be confused with the shorter, 19th century Gotthard Tunnel or the Gotthard Road Tunnel, this epic feat of engineering first opened in 2016 to boost train freight traffic beneath the Alps.

Passenger services between major Swiss and continental cities also zip through, passing depths of some 2,450 meters.

Lærdal Tunnel, Norway

Tunnels are essential in Norway, a means of connecting its many coastal cities and islands. The Lærdal Tunnel – or Lærdalstunnelen – is the longest road tunnel in the world, covering 24.5 kilometers (15.23 miles), and since 2000 has created the fastest route between Oslo and Bergen.

Aware that the 20-minute drive could cause motorists to lose concentration, engineers carved out rock chambers every six kilometers, with special blue and yellow lighting designed to mimic a sunrise.

Channel Tunnel, UK/France

Plans for an undersea connection between the UK and France date back over 200 years, with intrepid 19th-century engineers even trying to burrow beneath the English Channel to prove its viability.

The 50-kilometer (31-mile) tunnel first opened in 1994 following six years of construction work and sits some 75 meters (246 feet) beneath the sea bed.

Today the Channel Tunnel speeds passengers between London and Paris in just over two hours, with a car service allowing motorists and trucks to drive onto a train near UK coastal port Folkestone before disembarking at Calais on the French side.

Tokyo Bay Aqua-Line, Japan

Japan’s myriad islands and vast bays have long made it a mecca for tunnel makers. The Tokyo Bay Aqua-Line, also known as the Trans-Tokyo Bay Expressway, connects Kanagawa and Chiba prefectures, without the need to drive around the coast.

What makes it stand out, though, is the fact it starts out as a tunnel on the Kanagawa side, before rising out of the water at Umihotaru, an artificial island with a rest stop and viewing platforms for taking in sweeping views of the Tokyo skyline.

The final stretch to Chiba is covered on a bridge, which arrivals at Haneda airport will be able to spot as their plane comes in to land over the water.

Seikan Tunnel, Japan

The Gotthard Base Tunnel may have taken its crown as the longest railway tunnel in the world, but the Seikan Tunnel remains a remarkable feat of engineering, all 53.85 kilometers (33.46 miles) of it. It connects Honshu, the largest of Japan’s islands, with Hokkaido to the north.

First conceived in the 1950s in the wake of a series of ferry tragedies, today it’s used for passenger trains, including shinkansen bullet train services from Tokyo to Sapporo.

Even though domestic flights have cut the journey time dramatically, for incurable travel romantics, this remains the finest way to reach Japan’s magical far north.

Eisenhower Tunnel, Colorado

Taking cars, trucks and pickups from one side of the Great Divide to the other, the Eisenhower Tunnel is the highest vehicular tunnel in the United States. At 3,401 meters (11,158 feet) above sea level at its uppermost point, it’s not just the highest tunnel in the country, but also the highest on the entire Interstate system.

It’s actually made up of two tunnels, one named after President Eisenhower and the other after US Senator Edwin C. Johnson. The challenge of building across the continental divide meant fault lines were discovered during excavation.

Large Hadron Collider, France/Switzerland

Lying an average 100 meters beneath the border between France and Switzerland, the 27-kilometer (16.7-mile) long Large Hadron Collider forms a donut-shaped tunnel built expressly for particle acceleration. Particles are fired around the tunnel in two beams, which are then made to collide at four separate points.

Physicists have used this cutting-edge tunnel to learn more about the origin of mass, as well as puzzling out difficult questions about dark matter and dark energy.

You need special permission to enter as a visitor but can go above ground to CERN, the European Organization for Nuclear Research, which has a fascinating permanent exhibition about the collider’s work.

Jungfrau Railway, Switzerland

One of the great marvels of early 20th-century engineering, the Jungfrau Railway winds its way through a tunnel hewn into some of the most iconic mountains in the Swiss Alps.

It was first conceived by Adolf Guyer-Zeller in 1893 and completed in 1912. Setting out from Kleine Scheidegg, at 2,061 meters (6,762 feet) it climbs through a hand-cut tunnel into the depths of the Eiger, where two stations, Eigerwand and Eismeer, offer views from the north and east faces of the mountain.

Passengers can no longer disembark at Eigerwand, although climbers have long been known to use the infamous Stollenloch window, built to dispose of debris, to access the tunnel and pull themselves to safety.

Today, hardy souls can join guided tours through this terrifying opening out onto the most famous North Face of them all. The tunnel emerges at Jungfraujoch, between the summits of Jungfrau and Mönch, at 3,454 meters. That makes it the highest railway in Europe.

Bund Sightseeing Tunnel, China

There are cheaper ways to get between Shanghai’s historic Bund and the futuristic towers of Pudong. But this short jaunt beneath the Huangpu River on a Maglev train provides a uniquely trippy experience.

Strobe lighting and sound effects are meant to create the feeling of gliding through space. Whether that’s the actual response of travelers is down to personal preference, although there’s no denying it’s a truly out-there way of getting around China’s biggest city.

Natural Tunnel, Virginia

Most railway tunnels are the result of years of painstaking engineering and the endurance of brutal working conditions. Natural Tunnel, though, is the result of a far slower process.

Formed over a million years as a result of the limestone and bedrock being dissolved by groundwater, it’s 61 meters at its widest point and 24 meters at its highest.

That meant it was a prime spot for the South Atlantic and Ohio Railroad to build a train track through it in 1893. Today, the tunnel is the key attraction in the State Park that bears its name, with amazing camping grounds, hiking trails and superb canoeing all at hand for active travelers.

Glow Worm Tunnel, Australia

A remote, former railway tunnel in New South Wales’ Wollemi National Park, Glow Worm Tunnel takes its name from the gnat larvae that live on its roof and walls.

Trains haven’t passed this way since the 1940s, leaving the glow worms in peace to light up and draw in their prey.

The fact the tunnel curves almost 180 degrees makes for perfect, dark conditions for these fascinating creatures – visitors are advised to bring a torch to light the way. Today, hikers can walk into the tunnel after driving north from Lithgow.

Cu Chi Tunnels, Vietnam

This renowned network of tunnels on the outskirts of Ho Chi Minh City has long been a source of fascination for tourists looking to learn more about the war that ravaged Vietnam during the 1960s and 1970s.

Used as a base for Viet Cong attacks on US and South Vietnamese positions, the tunnels also served as living quarters and weapons stores.

Despite repeated attempts by American forces to destroy the vast network of 75 miles of tunnels, they survived and are now maintained as memorials by the Vietnamese government.

Visitors can get a taste of the claustrophobic spaces and even see where the 1968 Tet Offensive was planned.

SMART, Kuala Lumpur, Malaysia

Malaysian engineers struck upon a clever solution when weighing up how to divert stormwater away from the center of Kuala Lumpur as well as ease congestion on the city’s clogged roads: the stormwater management and road tunnel, aka SMART.

Consisting of a bypass tunnel for rainwater and a double-deck motorway, SMART became the world’s first dual-function tunnel when it opened in 2007.

If rain becomes so intense that the water tunnel is at capacity, then the road tunnel is also used to ease the flow of floodwater into the Taman Desa reservoir. In December 2021, SMART diverted a massive five million cubic meters of floodwater in the wake of a series of downpours in the Malaysian capital.

Guoliang Tunnel, China

Some tunnels burrow deep inside mountains to help get people from A to B. But in China’s Henan province, the Guoliang Tunnel takes an altogether more scenic route.

Cut just inside the vertiginous cliff faces of the Taihang Mountains, it has 30 windows that face out into the valley below, used for dumping rubble during construction. Just 13 locals from Guoliang built this scenic tunnel in a bid to make their village more accessible to the outside world.

Today it’s become one of China’s hottest tourist destinations, although those who drive it need a strong dose of gumption. Being carved by hand means it curves, dips and drops unexpectedly. And that’s before meeting cars coming in the opposite direction.

Langjokull Glacier Tunnel, Iceland

Billed as the largest manmade ice structure in the world, the Langjokull Glacier Tunnel winds its way deep into Iceland’s second-largest glacier, a two-hour drive from the capital Reykjavik.

The deeper visitors walk into the slippery depths, the more blue the ice becomes, its hue changing because of its age.

Guides are on hand to explain how the ice formed, what the future holds for these natural phenomena and to ensure no one takes a tumble (crampons are provided for strapping onto hiking boots)

Paris Catacombs, France

This vast network of limestone mines beneath Paris’s Left Bank dates back to the 12th century, when rocks were excavated for buildings across the French capital.

It wasn’t until the late 18th century, though, that they became an ossuary for the deposit of human remains from Paris’s overflowing cemeteries. Today, some six million bodies can be found in the catacombs, with bones stacked neatly throughout.

Partially opened to the public in 1874 and used by both the French Resistance and occupying Nazis in the 1940s, tourists can still officially visit a small section, where a sign warns visitors about entering “the Empire of Death.”

However, most of the network remains off-limits. Intrepid explorers are still known to travel underground for days at a time, accessing lesser-known sections via Metro tunnels and Left Bank basements.

Drammen Spiral Tunnel, Norway

First opened in 1961 and renovated in 2020, Drammen’s Spiral Tunnel isn’t your average point-to-point underground road.

As its name suggests, it winds its way up from its entrance some 50 meters above sea level through six loops in the shape of a helix, emerging at 180 meters, where visitors can take in views of the surrounding mountains and woodland.

Be sure to pick up a specially made Spiral Troll, made with coiled rope to mimic the tunnel itself.

Leake St Tunnel, UK

Running beneath Waterloo Station, just south of the Thames, Leake St is home to the largest legal graffiti wall in London.

Urban artists flock here to create one-off works that are soon sprayed over by the next wave of street art talent. The space has become so popular that it’s now home to an event space, a board game cafe and a series of pop-up restaurants.

Greenwich Foot Tunnel, London

When it first opened in 1902, the Greenwich Foot Tunnel served as a quick and safe way to get workers from south London to the busy docks that once lined the Isle of Dogs on the other side of the River Thames.

While many of those were destroyed during World War II, and the tunnel itself sustained damage from German bombs, it remains an easy way to cross the Thames in this part of London.

Access is via glass-domed buildings on either side of the water, both of which are showcases for the city’s superb, early 20th-century architecture.

Road of 52 tunnels, Italy

The Strada delle 52 Gallerie, or Road of 52 Tunnels, is one of the great military achievements of the 20th century. Built by Italian military personnel and local workers in just 10 months in 1917, it carves its way through Monte Pasubio and was designed to allow the passage of mules and men out of the range of Austrian artillery.

Today, each of the 52 tunnels can be passed through during a day-long hike. Take a guide to get the full lowdown on just how this amazing set of tunnels was completed in such short order.

Burro Schmidt Tunnel, California

Most tunnels have a purpose, whether it’s getting cars beneath treacherous bodies of water or offering trains a route through vast mountain ranges. But the Burro Schmidt Tunnel in the Mojave Desert, named after a local miner, is something of an enigma.

Dug by hand, with the help of the occasional stick of dynamite, Schmidt’s tunnel began in 1902 as a way of taking ore between the owner’s claimed land and a nearby smelter.

Yet when a road opened up in 1920 to ease such passage, he dug on anyway.

Finishing in 1938, Schmidt’s tunnel cut all the way through Copper Mountain before emerging on a remote and vertiginous ledge. Visitors can head to the cabin where the tunnel begins to try and puzzle out why this tunnel became such a singular obsession.

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