Top 15 Longest Tunnels in the World That Pushed Engineering Limits

The longest tunnels in the world show what engineers can achieve when geography gets in the way. They run through mountains, under cities, and even beneath the sea, solving challenges that surface routes cannot.

This article ranks the Top 15 world's longest tunnels by continuous length. Let’s look at the water, rail, road, drainage, and underwater tunnels that lead the global list in 2026.

Note: This ranking is based on continuous tunnel length using publicly available engineering and infrastructure data. It includes operational tunnels of all types, and placement may differ from category-based records such as “longest rail” or “longest road” tunnels.

1. Delaware Aqueduct: The World’s Longest Water Tunnel in New York

The Delaware Aqueduct stretches 85 miles (137 kilometers) beneath New York State, making it the longest tunnel in the world by continuous length. It delivers drinking water to New York City and carries roughly half of the city’s daily supply.

• Total length: 85 miles (137 km)
• Location: New York State, USA
• Type of tunnel: Water supply tunnel
• Route: Catskill-Delaware watershed to New York City
• Construction period: 1937-1945 (8 years)
• Estimated travel time: Varies by flow rate (water conveyance tunnel)
• Primary purpose: Municipal drinking water delivery
• Operator: NYC Department of Environmental Protection (DEP)

For more than a decade, the NYC Department of Environmental Protection (DEP) has led a roughly $1 billion effort to repair two major leaks in the Delaware Aqueduct.

At 137 km, the Delaware Aqueduct remains in a class of its own, far longer than even record-setting transport tunnels like Switzerland’s Gotthard Base Tunnel.

2. Päijänne Water Tunnel: Finland’s Hidden Freshwater Lifeline

The Päijänne Water Tunnel is the second-longest tunnel in the world, running 75 miles (120 kilometers) beneath southern Finland. It delivers raw freshwater from Lake Päijänne to the Helsinki region. For more than one million residents, it is Finland’s most impressive water supply link.

• Total length: 75 miles (120 km)
• Location: Southern Finland
• Type of tunnel: Water supply tunnel
• Route: Lake Päijänne to the Silvola reservoir near Helsinki
• Construction period: 1972-1982 (10 years)
• Estimated travel time: ~20-30 hours (gravity-fed water transfer)
• Primary purpose: Municipal drinking water delivery
• Operator: Helsinki Region Environmental Services (HSY)

Water is drawn from deep below the lake surface, helping it stay naturally cool year-round. The gentle downhill flow of the Päijänne Water Tunnel also allows small-scale hydropower generation, quietly improving the tunnel’s overall efficiency.

3. Dahuofang Water Tunnel: A Massive Water Diversion Megaproject in Liaoning

The Dahuofang Water Tunnel extends 53 miles (85.3 kilometers) beneath Liaoning Province and ranks among Asia’s longest water supply tunnels. With a diameter of roughly 8 meters, it is wide enough to resemble a rail passage more than a conventional pipeline.

• Total length: 53 miles (85.3 km)
• Location: Liaoning Province, China
• Type of tunnel: Water diversion and supply tunnel
• Route: Dahuofang Reservoir to Shenyang and surrounding cities
• Construction period: 2006-2009 (3 years)
• Estimated travel time: Several hours (controlled flow system)
• Primary purpose: Regional municipal and industrial water delivery
• Operator: Liaoning Runzhong Water Supply Co., Ltd.

Much of the Dahuofang Water Tunnel was excavated using tunnel boring machines (TBMs), enormous rotating systems that drill through rock while lining the tunnel. With more than 60 kilometers bored mechanically, the Dahuofang Water Tunnel remains one of the world’s longest TBM-driven water projects.

4. Orange-Fish River Tunnel: South Africa’s Landmark Water Transfer Megatunnel

The Orange–Fish River Tunnel carries water for 51 miles (82.8 kilometers) from the Gariep Dam into South Africa’s drier Eastern Cape. It has become a lifeline for towns, irrigation, and farming far beyond the river’s natural reach. The tunnel remains one of the country’s most important water transfer links.

• Total length: 51 miles (82.8 km)
• Location: South Africa
• Type of tunnel: Water transfer and supply tunnel
• Route: Orange River system (Gariep Dam) to the Fish River basin
• Construction period: 1966-1975 (9 years)
• Estimated travel time: ~1-2 days (high-volume gravity flow)
• Primary purpose: Irrigation and municipal water supply
• Operator: South African Department of Water and Sanitation

The construction of the Orange-Fish River Tunnel is extraordinary. Engineers removed nearly 2.5 million cubic meters of rock, enough to build two Empire State Buildings, and lined the tunnel with over 800,000 cubic meters of concrete. Today, the tunnel remains one of Africa’s most remarkable water megatunnels.

5. Bolmen Water Tunnel: Sweden’s Long-Range Aqueduct Below Ground

The Bolmen Water Tunnel runs 51 miles (82 kilometers) from Lake Bolmen toward the Scania region, helping supply one of the country’s most populated areas. It is one of Europe’s longest water tunnels, built purely for drinking water delivery.

• Total length: 51 miles (82 km)
• Location: Southern Sweden
• Type of tunnel: Water supply tunnel
• Route: Lake Bolmen to the Scania region
• Construction period: 1975-1987 (12 years)
• Estimated travel time: ~1 day (gravity-fed system)
• Primary purpose: Municipal drinking water delivery
• Operator: Sydvatten AB

By moving clean lake water through bedrock over long distances, the Bolmen Water Tunnel acts as a hidden supply artery for southern Sweden. Bolmen may lack the fame of major rail or underwater tunnels, but it remains one of Europe’s longest water tunnels and a vital piece of infrastructure.

6. Tùnel Emisor Oriente: Engineering Drainage on a Monumental Scale in Mexico City

Tùnel Emisor Oriente stretches 39 miles (62.5 kilometers) under Mexico City and serves as one of the capital’s most important flood-control tunnels. It carries wastewater away from a basin that has faced serious flooding for decades. It is one of the country’s most critical underground infrastructure projects.

• Total length: 39 miles (62.5 km)
• Location: Mexico City, Mexico
• Type of tunnel: Wastewater and drainage tunnel
• Route: Mexico City basin to regional discharge systems
• Construction period: 2009-2019 (10 years)
• Estimated travel time: Variable (storm-driven flow conditions)
• Primary purpose: Flood prevention and wastewater capacity
• Operator: National Water Commission (CONAGUA)

The construction of the Tùnel Emisor Oriente used some of the world’s largest earth-pressure-balance tunnel boring machines. They were built to cut through volcanic rock and soft clay along the same route. This long tunnel now plays a central role in protecting Mexico City during heavy rains.

7. Gotthard Base Tunnel: Breaking Records Through the Heart of the Swiss Alps

The Gotthard Base Tunnel runs 35 miles (57.1 kilometers) beneath the Swiss Alps and remains the world’s longest railway tunnel. Built between Erstfeld and Bodio, it anchors the New Rail Link through the Alps, Switzerland’s largest rail project. Often called an engineering “work of the century,” the tunnel took 17 years to complete.

• Total length: 35 miles (57.1 km)
• Location: Switzerland (Uri to Ticino)
• Type of tunnel: High-speed railway base tunnel
• Route: Erstfeld to Bodio
• Construction period: 1996-2016 (20 years)
• Estimated travel time: ~20 minutes
• Primary purpose: Passenger and freight rail through the Alps
• Operator: Swiss Federal Railways (SBB)

Trains pass through the tunnel in about 20 minutes at speeds up to 250 km/h, cutting Zurich–Milan travel time by nearly an hour. Opened in 2016 with European leaders in attendance, the tunnel’s debut even featured a uniquely Swiss celebration with music and yodeling.

💡Fun fact: the Gotthard Base Tunnel contains 3,200 kilometers of copper cable, enough to stretch across much of Europe.

8. Seikan Tunnel: The Longest Underwater Tunnel Between Japanese Islands

The Seikan Tunnel dives 33 miles (53.9 kilometers) beneath Japan’s Tsugaru Strait, linking Honshu and Hokkaido by rail. Its tracks lie about 140 meters below the seabed, making it the longest undersea rail tunnel in the world.

• Total length: 33 miles (53.9 km)
• Location: Japan (Honshu to Hokkaido)
• Type of tunnel: Undersea railway tunnel
• Route: Aomori Prefecture to Hokkaido Island
• Construction period: 1971-1988 (17 years)
• Estimated travel time: ~50 minutes
• Primary purpose: Passenger and freight rail connection
• Operator: JR Hokkaido

The Seikan Tunnel is both long and incredibly deep. About 50 trains pass through each day, supported by emergency stations built beneath the ocean floor.

It held the railway length record until the Gotthard Base Tunnel surpassed it in 2016. Today, the Seikan Tunnel remains one of the world’s most famous tunnels ever built beneath the sea.

9. Channel Tunnel: The Iconic Underwater Link Between Britain and France

The Channel Tunnel, often called the Chunnel, stretches 31 miles (50.5 kilometers) under the English Channel and includes the world’s longest undersea tunnel section at nearly 38 kilometers below the seabed. It created a direct rail connection between Britain and mainland Europe.

• Total length: 31 miles (50.5 km)
• Location: United Kingdom and France
• Type of tunnel: Undersea railway tunnel
• Route: Folkestone (Kent) to Coquelles (Pas-de-Calais)
• Construction period: 1987-1994 (7 years)
• Estimated travel time: ~35 minutes
• Primary purpose: Passenger and freight rail link
• Operator: Getlink (Eurotunnel)

Opened in 1994, the Channel Tunnel became one of Europe’s defining megaprojects. Built with three parallel bores and a central service tunnel, it was designed for constant, high-volume traffic. The tunnel now carries a significant share of UK-EU trade each year.

On January 23, 2026, the first electric heavy goods vehicle crossed on a LeShuttle freight train, supporting lower-emission freight through the Channel Tunnel.

10. Yulhyeon Tunnel: A Landmark Rail Tunnel Beneath South Korea’s Urban Belt

The Yulhyeon Tunnel extends 31 miles (50.3 kilometers) through Gyeonggi Province and is both South Korea’s longest railway tunnel and the fourth-longest railway tunnel in the world. It forms the main underground stretch of the Suseo High-Speed Railway near Seoul.

• Total length: 31 miles (50.3 km)
• Location: Gyeonggi Province, South Korea
• Type of tunnel: High-speed railway tunnel
• Route: Suseo (Seoul) to Pyeongtaek corridor
• Construction period: 2011-2016 (5 years)
• Estimated travel time: ~15-18 minutes
• Primary purpose: Passenger high-speed rail transport
• Operator: Korea Rail Network Authority / SR

Designed for speeds up to 300 km/h, the double-track tunnel allows fast travel beneath South Korea’s expanding metropolitan belt.

Engineers built the Yulhyeon Tunnel using the New Austrian Tunnelling Method (NATM), a technique suited for complex ground conditions. The tunnel shows how today’s longest rail tunnels are often shaped by cities, not mountains.

11. Songshan Lake Tunnel: Urban Rail Beneath Guangdong’s Growth Corridor

The Songshan Lake Tunnel stretches 24 miles (38.8 kilometers) beneath Guangdong, cutting through one of China’s fastest-growing industrial regions. It is part of the Dongguan–Huizhou Intercity Railway. The route helps connect suburbs, factories, and major business hubs across the Pearl River Delta.

• Total length: 24 miles (38.8 km)
• Location: Guangdong Province, China
• Type of tunnel: Urban and intercity railway tunnel
• Route: Jiao Station to Changping East Station (Dongguan–Huizhou line)
• Construction period: 2013-2016 (3 years)
• Estimated travel time: ~20 minutes
• Primary purpose: Passenger and goods rail transport
• Operator: China Railway / regional intercity rail services

Trains move through the Songshan Lake Tunnel at speeds up to 200 km/h, with underground stations built directly along the alignment. Built with stations along its route, the tunnel feels less like a remote engineering feat and more like a working piece of the city.

12. Lötschberg Base Tunnel: Driving Modern Rail Beneath the Bernese Alps

The Lötschberg Base Tunnel spans 22 miles (34.6 kilometers) beneath the Bernese Alps and ranks as the third-longest railway tunnel in Europe. It plays a major role in Switzerland’s north-south freight and passenger corridor. The Channel Tunnel is longer at 50.5 km, but Lötschberg remains a key Alpine link.

• Total length: 22 miles (34.6 km)
• Location: Switzerland (Bernese Alps)
• Type of tunnel: Railway base tunnel
• Route: Frutigen area to Raron valley corridor
• Construction period: 1999-2007 (8 years)
• Estimated travel time: ~15 minutes
• Primary purpose: Passenger and freight rail through the Alps
• Operator: BLS AG

Two tubes were excavated between Ferden and Mitholz, but parts of the tunnel initially opened as a single track to manage costs, creating a phased approach to capacity.

As of January 19, 2026, expansion through 2035 is underway to add more double-track sections and improve reliability. The Lötschberg Base Tunnel remains one of Europe’s most important modern rail tunnels.

13. New Guanjiao Tunnel: A High-Altitude Railway Tunnel Crossing the Tibetan Plateau

The New Guanjiao Tunnel cuts through the Guanjiao Mountains for 20 miles (32.6 kilometers). Built at elevations above 3,300 meters, it is the world’s longest high-altitude railway tunnel. Few tunnels combine this length with such thin air and harsh terrain.

• Total length: 20 miles (32.6 km)
• Location: Qinghai Province, China
• Type of tunnel: High-altitude railway tunnel
• Route: Xining-Golmud Railway corridor (Guanjiao Mountain section)
• Construction period: 2007-2014 (7 years)
• Estimated travel time: ~25 minutes
• Primary purpose: Rail transport across the Tibetan Plateau region
• Operator: China Railway

The twin-bore New Guanjiao Tunnel earned international recognition for the challenge of building at extreme altitude. While India’s Atal Tunnel holds the altitude record for long road tunnels at 9 km, Guanjiao pushes much farther in scale. It remains the world’s longest high-altitude railway tunnel, crossing terrain where rail construction is rarely possible.

14. Guadarrama Tunnel: Spain’s Longest Rail Link Through the Sierra Mountains

The Guadarrama Tunnel runs 18 miles (28.4 kilometers) through the Sierra de Guadarrama just north of Madrid. It is the longest railway tunnel in Spain and a key part of the Madrid–Valladolid high-speed corridor. The tunnel was designed for Alta Velocidad Española (AVE) trains traveling up to 310 km/h.

• Total length: 18 miles (28.4 km)
• Location: Spain (Sierra de Guadarrama, north of Madrid)
• Type of tunnel: High-speed railway tunnel
• Route: Madrid–Valladolid rail corridor
• Construction period: 2002-2007 (5 years)
• Estimated travel time: ~10-12 minutes
• Primary purpose: Passenger high-speed rail transport
• Operator: ADIF (Spanish rail infrastructure manager)

One of the Guadarrama Tunnel’s most distinctive features is its ventilation. Engineers eliminated intermediate shafts and instead relied on portal-based airflow, refined through detailed simulations. This long tunnel helped turn Madrid-Segovia trips into journeys of just minutes.

15. Lærdal Tunnel: Driving Through the Longest Road Tunnel in Norway

The Lærdal Tunnel stretches 15 miles (24.5 kilometers) between Lærdal and Aurland and is the longest road tunnel in the world. Drivers spend about 20 minutes underground without daylight. It forms a vital highway link between Oslo and Bergen through Norway’s rugged fjord landscape.

• Total length: 15 miles (24.5 km)
• Location: Norway (between Lærdal and Aurland)
• Type of tunnel: Road tunnel
• Route: Lærdal to Aurland on the Oslo-Bergen highway corridor
• Construction period: 1995-2000 (5 years)
• Estimated travel time: ~20 minutes (continuous drive)
• Primary purpose: Road transport through mountainous terrain
• Operator: Norwegian Public Roads Administration

What makes the drive memorable is the tunnel’s interior design. Engineers worked with psychologists to reduce monotony and improve safety. Three large caverns are lit in soft blue and warm tones that mimic sunrise. These “light rooms” make the Lærdal Tunnel one of the most memorable driving tunnels in the world.

Building Below Ground: How Long Tunnels Keep the World Moving

Several major projects under construction, such as the Brenner Base Tunnel, may soon surpass the longest tunnels in the world. These underground systems continue to expand as cities grow, rail networks modernize, and climate pressures increase the need for resilient infrastructure.

From water lifelines to high-speed rail links, these tunnels support daily life on a massive scale. They shorten travel routes, overcome natural barriers, and move essential resources where surface connections fall short. The world’s longest tunnels are more than engineering records; they are critical infrastructure that keeps modern societies running below ground.