<strong>SMART, Malaysia: </strong>This road tunnel in the Malaysian capital Kuala Lumpur also doubles as a storm drain to keep the city safe from flooding.
SMART, Malaysia: This road tunnel in the Malaysian capital Kuala Lumpur also doubles as a storm drain to keep the city safe from flooding.
Aizuddin Saad
<strong>Lærdal Tunnel, Norway:</strong> Stretching 15.2 miles, the Lærdal is the world's longest road tunnel.
Lærdal Tunnel, Norway: Stretching 15.2 miles, the Lærdal is the world's longest road tunnel.
Grigory Bruev/Adobe Stock
<strong>Guoliang Tunnel, China:</strong> Cut into the vertiginous cliff faces of the Taihang Mountains, this tunnel was originally built by locals to make Guoliang village more accessible. Today it's a top tourist destination.<br />
Guoliang Tunnel, China: Cut into the vertiginous cliff faces of the Taihang Mountains, this tunnel was originally built by locals to make Guoliang village more accessible. Today it's a top tourist destination.
Fei/Adobe Stock
<strong>Large Hadron Collider, France/Switzerland: </strong>A donut-shaped tunnel beneath the border between France and Switzerland houses extraordinary research into dark matter.<br />
Large Hadron Collider, France/Switzerland: A donut-shaped tunnel beneath the border between France and Switzerland houses extraordinary research into dark matter.
Valentin Flauraud/AFP/Getty Images
<strong>Burro Schmidt Tunnel, California: </strong>This tunnel in the Mojave Desert is named for the local miner who began work on it to transport ore. It was completed decades later even though a quicker road was built in the meantime.
Burro Schmidt Tunnel, California: This tunnel in the Mojave Desert is named for the local miner who began work on it to transport ore. It was completed decades later even though a quicker road was built in the meantime.
Julius Mueller/Moment RF/Getty Images
<strong>Tokyo Bay Aqua-Line, Japan: </strong>Also known as the Trans-Tokyo Bay Expressway, this route starts out as a tunnel before emerging via an artificial island to a bridge and causeway.
Tokyo Bay Aqua-Line, Japan: Also known as the Trans-Tokyo Bay Expressway, this route starts out as a tunnel before emerging via an artificial island to a bridge and causeway.
Kyodo News/Getty Images
<strong>Paris Catacombs, France: </strong>Originally dug out to provide stones for buildings across Paris, the catacombs were used in the 18th century as a place to store bones from the city's overflowing cemeteries.
Paris Catacombs, France: Originally dug out to provide stones for buildings across Paris, the catacombs were used in the 18th century as a place to store bones from the city's overflowing cemeteries.
Bony/SIPA/AP
<strong>Seikan Tunnel, Japan: </strong>This 33-mile tunnel connects Honshu, Japan's largest island, with Hokkaido to the north.
Seikan Tunnel, Japan: This 33-mile tunnel connects Honshu, Japan's largest island, with Hokkaido to the north.
Kyodo News/Getty Images
<strong>Glow worm tunnel, Australia: </strong>This disused railway tunnel in New South Wales' Wollemi National Park provides a perfect haven for glow worms.
Glow worm tunnel, Australia: This disused railway tunnel in New South Wales' Wollemi National Park provides a perfect haven for glow worms.
Santiago/Adobe Stock
<strong>Road of 52 Tunnels, Italy: </strong>Built in just 10 months during the end of World War I, this tunnel was designed to keep mules and men safe from Austrian artillery.
Road of 52 Tunnels, Italy: Built in just 10 months during the end of World War I, this tunnel was designed to keep mules and men safe from Austrian artillery.
starmaro/Adobe Stock
<strong>Greenwich Foot Tunnel, UK: </strong>Dug beneath London's River Thames, this foot tunnel once carried workers to busy docklands.
Greenwich Foot Tunnel, UK: Dug beneath London's River Thames, this foot tunnel once carried workers to busy docklands.
Alberto Pezzali/Pacific Press/LightRocket/Getty Images
<strong>Eisenhower Tunnel, Colorado:</strong> Built at 11,158 feet above sea level, this tunnel -- and its twin, the Johnson Tunnel, cross the Great Divide in the Rocky Mountains.
Eisenhower Tunnel, Colorado: Built at 11,158 feet above sea level, this tunnel -- and its twin, the Johnson Tunnel, cross the Great Divide in the Rocky Mountains.
David Zalubowski/AP
<strong>Bund Sightseeing Tunnel, China: </strong>This levitating train, with added illuminations, provides a link between Shanghai's historic Bund waterfront and the city's modern Pudong district.
Bund Sightseeing Tunnel, China: This levitating train, with added illuminations, provides a link between Shanghai's historic Bund waterfront and the city's modern Pudong district.
Rudi Ernst/Adobe Stock
<strong>Leake Street Tunnel, UK: </strong>This tunnel in south London is home to the largest graffiti wall in London and is a magnet for urban artists.
Leake Street Tunnel, UK: This tunnel in south London is home to the largest graffiti wall in London and is a magnet for urban artists.
Mike Kemp/In Pictures/Getty Images
<strong>Cu Chi Tunnels, Vietnam: </strong>Now a tourist attraction, this huge network of tunnels on the outskirts of Ho Chi Minh City was used as a base for Viet Cong attacks on US and South Vietnamese positions during the Vietnam War.
Cu Chi Tunnels, Vietnam: Now a tourist attraction, this huge network of tunnels on the outskirts of Ho Chi Minh City was used as a base for Viet Cong attacks on US and South Vietnamese positions during the Vietnam War.
hecke71/Adobe Stock
<strong>Drammen Spiral Tunnel, Norway: </strong>This road tunnel rises through the Norwegian mountains via six helix loops.
Drammen Spiral Tunnel, Norway: This road tunnel rises through the Norwegian mountains via six helix loops.
Tomasz Majewski
<strong>Channel Tunnel, France/UK: </strong>Opened in 1994, this 31-mile tunnel carries passengers and vehicles under the English Channel, creating a fast connection between Britain and mainland Europe.
Channel Tunnel, France/UK: Opened in 1994, this 31-mile tunnel carries passengers and vehicles under the English Channel, creating a fast connection between Britain and mainland Europe.
Denis Charlet/AFP/Getty Images
<strong>Gotthard Base Tunnel, Switzerland:</strong> This is the longest and deepest railway tunnel in the world, stretching more than 35 miles beneath the Alps.
Gotthard Base Tunnel, Switzerland: This is the longest and deepest railway tunnel in the world, stretching more than 35 miles beneath the Alps.
Swiss Travel System AG/obs/AP
<strong>Natural Tunnel, Virginia:</strong> Formed over a million years as a result of the limestone and bedrock being dissolved by groundwater, this railway tunnel is now a key attraction in a state park named for it.
Natural Tunnel, Virginia: Formed over a million years as a result of the limestone and bedrock being dissolved by groundwater, this railway tunnel is now a key attraction in a state park named for it.
Tim Pennington /iStockphoto/Getty Images
<strong>Langjokull Glacier Tunnel, Iceland:</strong> 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.
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.
LightFieldStudios/iStockphoto/Getty Images