The audacious underground mega tunnels redrawing the railway map of Europe

By Ben Jones, CNN

(CNN) — Europe wants to lure more people away from short-haul airlines and onto high-speed trains between its major cities. And as more and more travelers discover the joys of long-distance rail, there’s everything to play for.

But there’s one big problem: geography. Europe is a continent with mountain ranges slicing through it and seas severing countries from each other. And unlike planes, trains can’t simply skim over it all.

That’s why some of the world’s biggest and most daring construction projects are currently cutting, drilling and blasting their way through mountains that were once traversed only by the brave or the foolhardy.

The next decade will see the world’s longest rail tunnels completed in Austria, France and Italy, with the aim of revolutionizing rail connectivity between northern Europe and the industrial hubs of northern Italy. Billions of dollars are being invested in record-breaking tunnels and new approach lines to raise speeds and increase freight capacity on long-established corridors through the Alps.

Meanwhile, Denmark has long been tackling the seas, transforming rail and road travel with a chain of tunnels, artificial islands and soaring bridges linking its two biggest islands with mainland Europe and Sweden. In the early 2030s it will complete another road-rail link under the Baltic Sea to Germany, drastically shortening journey times between Copenhagen, Hamburg and Berlin.

And an even more ambitious plan to link Helsinki with Tallinn in Estonia and the other Baltic States via a 50-mile tunnel under the Gulf of Finland has also been proposed.

That’s the plan, at least. But creating the world’s longest rail tunnels is technically challenging and ferociously expensive, and Europe’s recent record of delivery is best described as “patchy.”

To no one’s surprise, construction costs have ballooned and delays are measured in years, or even decades, which means that the European Union will not meet its deadline of completing the core Trans-European Transport Network (TEN-T) — the ambitious project to upgrade 10,850 miles of rail corridors across the continent by 2030, linking major cities, regions and ports.

In January, the European Court of Auditors reported that the costs of delivering eight major TEN-T projects have increased by an average of 82% over their initial estimates. The average delay across five projects is 17 years.

However, it’s not all doom and gloom. EU member states see infrastructure investment as a key stimulus for economic prosperity and sustainable mobility. And these new mega-tunnels will revolutionize international travel within the next decade, knitting together regions and countries that have until now been separated by mountains and seas.

“Mega-projects like the Brenner Base Tunnel, Lyon–Turin and the Fehmarn Belt can be game-changers for European rail,” says Nick Brooks, secretary general of rail operator lobby group ALLRAIL.

Here are some of the most exciting projects underway.

Beating a natural border

For centuries the Alps have been a natural border separating northern and southern Europe. The high mountains were a land of mythical beasts and potentially lethal weather — a place to be feared and, if possible, avoided. From the 18th century, wealthy “Grand Tourists” from northern Europe hired sedan chairs and local guides to negotiate the treacherous Alpine passes on their way to Italy. Gradually the trails became roads — but they were still dangerous and often closed by snow for much of the year.

In the late 1800s and early 1900s, the first generation of Alpine rail tunnels pushed the limits of civil engineering and rail technology to create the first all-weather routes through the mountains. To keep the tunnels as short as possible — although they were still among the world’s longest for many decades — these early links were still at relatively high altitudes, requiring long, steep approach climbs. To gain height, armies of workers drilled and blasted their way through hostile terrain using every trick at their disposal. Even today, their tracks weave through the mountains, hug contours and leap across valleys on spectacular bridges, making them tourist attractions in their own right.

But for train companies, they have always been difficult and expensive to operate. Not only are they vulnerable to rockfalls, landslips and extreme weather but they are slow, inefficient and increasingly lacking the capacity for modern traffic.

The solution: new tunnels at lower altitudes. Known as base tunnels, they bypass the sinuous mountain routes, allowing more trains to run at faster speeds.

Leading the pack is the 35-mile Gotthard Base Tunnel (GBT) in Switzerland, which opened in 2016. Everything about this $11.3 billion project — which connects the cantons of Ticino and Uri, and lies on the busy Zürich-Milan route — is on a grand scale. At their deepest point, the GBT’s twin tunnels are more than 7,500 feet below the Alpine peaks — or nearly a mile and a half down. Journey times for international travelers between Zürich and Milan have been slashed to just two and a half hours, compared with four hours via the old Gotthard route, which is 25 miles longer and pierces the mountains at an altitude of 3,773 feet.

The GBT is part of a wider international project, officially known as Neue Eisenbahn Alpentransversale (NEAT) or New Trans-Alpine Railways, to provide flatter, high-capacity rail links between northern Europe and Italy. As well as the GBT, the 21.5-mile Lötschberg Base Tunnel opened under the Bernese Alps in 2007. Part of the main route from North Sea ports and Germany to northern Italy’s industrial Lombardy region, it lies 1,300 feet below the original Lötschberg tunnel, which had opened in 1913.

En route: the world’s longest rail tunnel

Switzerland’s achievements are inspiring other countries. Austria is also in a strategic location between Europe’s industrial hubs, and has embarked on a similarly ambitious program of tunnel-building to liberate its Alpine valleys from heavy freight traffic. Tens of billions of dollars are being invested in base tunnels and massive upgrades of the main rail routes linking them to Germany and Italy.

Linking Innsbruck in Austria and Bolzano in Italy, the Brenner Pass has long been the primary trade route between wealthy southern Germany and northern Italy. The route has been popular since Roman times, but will soon get a serious upgrade with the forthcoming Brenner Base Tunnel (BBT), scheduled to open in 2032.

Work to excavate more than 140 miles of new tunnels for the BBT system is almost complete, including almost 65 miles of rail tunnels and 30 miles of subterranean approach lines. The core of the BBT project is two parallel 34-mile-long rail tunnels between the outskirts of Innsbruck and Franzenfeste/Fortezza in Italy’s bilingual South Tyrol region. The tunnels bypassing Innsbruck were opened in 1994 — that’s how slow time moves on these mega-tunnel projects.

As with many major infrastructure projects around the world, construction of the BBT has taken much longer than expected; work began in 1999, when it was expected to open in 2015. Coming in at an estimated $9.9 billion, it will cost almost double the original estimate.

When it opens in 2032 the BBT — which will extend under the mountains for nearly 35 miles — will be second only in length to the Gotthard Base Tunnel, but its network of approach tunnels make it a much longer and more complex project. It will provide a flatter, faster and more direct route under the Tyrolean Alps, cutting trips between Innsbruck and Bolzano from two hours to just 50 minutes.

South of Vienna, the oldest and most celebrated railway across the Alps is also being bypassed. The 17-mile, $5 billion Semmering Base Tunnel will complete a new, fast route from the Austrian capital to the southern cities of Graz and Villach, and onward to Italy, Slovenia and the Adriatic when it opens in 2030. The iconic Semmeringbahn, or Semmering Railway, was the first to cross the Alps when it opened between 1848 and 1854. It is now a UNESCO World Heritage Site but is increasingly unsuitable for modern requirements.

In combination with the new 81-mile Koralm Railway between Graz and Villach, which opened in December 2025 and includes Austria’s current longest tunnel (20.4 miles), the Semmering Base Tunnel route will slash journey times between three of Austria’s most important rail hubs and deliver a faster, more efficient high-capacity link in the Baltic Sea-Adriatic Sea Corridor of the TEN-T Network.

Setbacks in France

Projects of this magnitude are not without their critics or difficulties though. All these new tunnels are being delivered later than planned and costing significantly more than expected. Most have their opponents too, whether political, environmental or from communities affected by the work.

Perhaps the starkest example of this is the controversial 170-mile railway linking Lyon in France with Turin in northern Italy. At the heart of this international mega-project is the $14 billion, 36-mile Mont Cenis (or Mont D’Ambin) Base Tunnel to replace another challenging mountain railway through the French Alps.

Although the Mont Cenis road route, once popular with Grand Tourists, is always busy with trucks, the rail line is currently underused by freight. More than 90% of freight between France and Italy moves by road. Poor reliability on both sides of the border and lengthy line closures caused by landslips have caused freighters to abandon rail.

The new base tunnel aims to change that, however. The project’s ambition is eventually replace around one million heavy vehicle trips per year and achieve a 50:50 split between road and rail traffic, although no date is given for when that might be achieved. It also aims to nearly quadruple international passenger services, from six to 22 trains per day. Once separate projects to upgrade links to the French and Italian high-speed rail networks on each side are complete — which could be another 20 years — Paris to Milan journeys could be cut from seven hours to just four. Maximum freight train loads could double, to 2,500 tonnes, but energy consumption will be reduced by 40% due to the flatter profile of the new route.

However, legal challenges, political opposition and protests, occasionally violent in nature, have beset this project from the outset, particularly on the Italian side. Civil engineering work started as far back as 2002, although tunneling did not commence until 2016.

Even then, some especially difficult geology on the French side meant that modern tunnel boring machines could not be used — workers had to resort to traditional drilling and blasting methods. Since 2020, construction costs for the full project have increased by 23% to $17.7 billion and the completion date has been pushed back to 2033 — 18 years later than originally planned. Worryingly, construction of the new approach lines from Lyon and Turin towards the tunnel has not yet commenced in any meaningful sense, and reports suggest that those on the French side may not be ready until 2045. Without these, it will be impossible to exploit the full value of the core tunnels as capacity and train speeds on existing lines will still be severely limited.

“There’s no doubt that these cross-border rail links have the potential to transform the amount of passenger and freight traffic moving by rail across the continent,” says Nick Kingsley, executive editor of Railway Gazette International. “However, while the core sections get all the attention and in many cases are making good progress in construction, the challenge is completing the connecting lines.”

While the BBT approach lines on Austrian territory are complete, Germany has so far failed to honour its commitment to build new high-capacity lines across the southern Bavaria area to link with them. Likewise, schemes to build new dedicated freight lines through southwest Germany to link with the Gotthard and Lötschberg base tunnels are running decades behind schedule, similar to the delays in France on the Mont Cenis project.

“It is likely that the Brenner and Mont Cenis tunnels will be ready for use long before the new lines funnelling trains into them from Germany and France,” says Kingsley.

“Funding, defining and delivering the approach routes in the various member states is arguably the biggest challenge in ensuring these various rail mega-projects are a success.”

Under the sea

Europe’s tunneling revolution isn’t only taking place under mountains, however — there are developments underwater, too. The $9 billion Fehmarnbelt tunnel between Germany and Denmark will enable much faster and more frequent international services between major cities. Running between the German island of Fehmarn, north of Lübeck, and the Danish island of Lolland, which is already connected to Copenhagen’s island, the Fehmarnbelt is due to open its road link in 2031, three years later than planned, the the rail link to follow. It will use submerged tubes laid on the floor of the Baltic Sea to carry trains and road traffic 12 miles between the two countries, slashing up to two hours and more than 100 miles off existing Hamburg-Copenhagen railway links.

Completely rebuilt and electrified 125mph approach lines on both sides will transform journeys between Germany and Denmark and open up new possibilities for onward travel by rail into Sweden via the spectacular Øresund Bridge, which opened in 2000.

It’s not all good news

While the future may look bright for those wishing to travel around Europe via high-speed rail, it also looks expensive. International train travel on the continent is usually considerably more expensive than flying with a budget airline.

“Concrete and steel alone won’t deliver better journeys,” says ALLRAIL’s Nick Brooks. “To give any new infrastructure the highest return on investment, the EU needs genuine high-speed competition on the tracks, with impartial ticket retail on dominant ticketing platforms, long-term access certainty, fair track access charges and equal access to rolling stock and finance, so that multiple operators — both independent and state-owned incumbent carriers — can fully use the new capacity.

“If the conditions above are put in place, these projects will deliver faster journeys, more trains, lower fares and better cross-border connections. Without them, there is a real risk that the mega-projects remain underused rather than transformative.”

The next step for the EU is to create a 35,000-mile pan-European high-speed rail network linking all of its capitals and major cities by 2050. According to the Community of European Railways, this would mean at least tripling the existing European HSR network at an estimated cost of around $650 billion — though it would create net positive benefits to society in the range of $886 billion within 20 years.

Achieving it will require massive investment, political will and international cooperation.

But perhaps most challenging of all, it will depend on faster, safer and more direct railways overcoming the natural obstacles that have divided communities for millennia.

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