Trains are often described as one of the more gentle ways of travelling at a slower pace, taking in gorgeous scenery you wouldn't be able to see any other way. But there are routes in the world that do quite the opposite. Whether they're hair-raisingly fast, crossing spine-tingling bridges and viaducts or appearing to dangle in air, these trains offer rides that are anything but relaxing. Prepare for an adrenaline rush as we take a look at the world's most terrifying train journeys.

Aptly named Train to the Clouds, or Tren a las Nubes, this thrilling service is Argentina's most famous. Departing once a week from Salta, the train passes through tobacco fields and past cattle ranches, taking in 29 bridges, 21 tunnels and 13 viaducts. The most thrilling part of the 16-hour journey is the viaduct that spans the width of a desert canyon in La Polvorilla. Here, the train climbs to an altitude of 13,845 feet (4,220m), which makes it the sixth highest railway in the world. These days large parts of this stunning journey are done by bus.

The Durango & Silverton Narrow Gauge Railroad frequently finds itself among lists of the world’s greatest train journeys – and it’s not hard to see why. On the 45-mile (72km) route, the train crosses the Animas River five times and winds its way through canyons in the stark wilderness of the San Juan National Forest. Often chugging along narrow mountainsides and right along the riverbank, it's both a stunning and spine-tingling journey.

One of India's many mountain railways, this narrow-gauge route between Kalka and Shimla in northern India was built in the late 19th century for the British Raj. The train traverses dramatic landscape and crosses an impressive 864 bridges as well as 102 tunnels, all of which date back to when the line was finished. Several sections along the route follow the crest of the mountain with ominous drops and dramatic views appearing as the train dips in and out of tunnels.

This notable route might not seem that scary at all – apart from rickety wooden bridges and tracks clinging on to cliffsides – but it's actually the history of it that makes for an unsettling journey. Dubbed the Death Railway, it was constructed by around 180,000 civilian labourers and 60,000 Allied prisoners of war in 1943, of whom more than 40% died as a direct result of the project. Its most famous portion is Bridge 277, known as the Bridge on the River Kwai. Today, only a section of the route in Thailand survives and is a popular activity for visitors to Kanchanaburi.

Considered one of the steepest rail trips in the world, this short journey through the Ecuadorian Andes is a dramatic and treacherous one. Connecting Alausi and Sibambe, the train zig-zags up the mountain known as Nariz del Diablo, or the Devil's Nose. Ascending nearly 2,000 feet (609m) in just seven miles (11km), from 5,905 feet (1,799m) to 7,545 feet (2,299m), the train is an engineering marvel. And while it's no longer possible to sit on the roof of the carriage like in the early 20th century, it's still an unsettling ride.

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Often described as one of the most beautiful train rides in the world, this journey is just under two hours and takes in some of the most beautiful scenery Norway has to offer. It's also one of the steepest non-rack railways in the world, travelling from sea level at the Sognefjord in Flåm to the Myrdal mountain station, 2,841 feet (866m) above sea level. Many tunnels, one of which is a spiral, and waterfall spray washing over the train all make for a pretty stomach-churning ride.

The two-hour journey on the Kuranda Scenic Railway begins in Cairns and takes visitors through one of the world's oldest rainforests. The tropical scenery is made up of lush vegetation, mountains and ravines as well as an impressive waterfall, Barron Gorge. The train chugs along a spine-tingling viaduct that appears to be floating among the canopy to bring its passengers the best views of this special place.

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The railroad has its roots in the Klondike Gold Rush of the late 19th century, when it was constructed to help gold prospectors get out of Skagway and into Canada. Today, the 110-mile (177km) stretch can be travelled in vintage cars via two excursions. On the journey, passengers take in a panorama of mountains, glaciers, gorges and waterfalls. The two-and-a-half-hour Summit Excursion retraces the original route to the White Pass Summit, 3,000 feet (914m) above sea level along a route peppered with tunnels, rickety wooden bridges and tracks built into the mountainside.

India's only rack railway, the Nilgiri Mountain Railway from Mettupalayam to Udagamandalam is part of the UNESCO-listed Mountain Railways of India but the gorgeous views come at a slightly unsettling price. The train climbs the mountain rather sharply – it has the steepest track in Asia with a maximum gradient of 8.33%. The route takes exactly 290 minutes to go uphill, yet the return journey is 75 minutes shorter.

Connecting two of Switzerland's mountain resorts, Zermatt and St Moritz, Glacier Express is a brilliant way of seeing some of the most beautiful views in the Swiss Alps. The scenic but slightly scary route takes in sights like Oberalp Pass, the highest point of the journey, and the Landwasser Viaduct – a six-arch bridge which stands at 213 feet (65m) and plunges straight into a tunnel that leads through the mountain. The day-long trip covers 91 tunnels, 291 bridges and offers the chance to take in stunning alpine meadows, mountain lakes and chalets. 

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The country's first sea bridge, the Pamban Bridge, connects Rameswaram island to Chennai on the mainland. With not much else around the track, it can certainly start to feel as if the train is just gliding on water along this nearly mile-long (1.4km) bridge. Constructed in 1914, there's also a drawbridge section along the route to allow boats and ships to pass. Harsh weather is also a factor here – during sea storms, the tracks and trains tremble in the wind, giving passengers a huge scare. In 1964, a cyclone caused huge tidal waves that washed away a train on the bridge.

As the name suggests, this breathtaking train journey leads its passengers through the mighty Denali National Park. The Alaska Railroad's flagship train, Denali Star embarks on a 12-hour ride between Anchorage and Fairbanks via Wasilla, Talkeetna and Denali. Along the 365-mile (587km) journey, the train rushes past rivers and mountains and offers expansive panoramas of Hurricane Gulch from the top of a terrifying 296-foot (90.2m) bridge. It's all worth it for the views, though.

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Travelling on a three-hour journey between Indonesia's capital Jakarta and Bandung, capital of West Java province, the train lets its passengers marvel at beautiful views of tea plantations, small towns and mountain scenery. However, the relaxing ride soon becomes quite unsettling as the train approaches the sky-high Cikurutug pylon trestle bridge. With terrifying drops on both sides, the bridge doesn't have barriers on either side and it's easy to feel like you're about to go off it at any moment. 

The steepest cogwheel railway in the world, this train, ferrying passengers up to the summit of Mount Pilatus, is no mean feat. Reaching a maximum gradient of up to 48% it can be a challenging journey as it feels like the train is about to topple over any second. The track's steep gradient is not its only spine-chilling feature. Clinging on to the mountainside, the train passes through tunnels carved into the mountain which open up to sweeping views of the surrounding landscape. Don't look down if you're afraid of heights though.

Much of this train journey is nothing but undulating fields and small villages, that is until travellers catch the first glimpse of the Gokteik viaduct and the adrenaline rush starts. Opened in 1900, it was the largest railway trestle bridge in the world and today its 820-foot (250m) height will still set pulses racing. Certainly not one for the faint-hearted, the bridge is slightly curved and measures nearly 2,300 feet (700m) in length so the train slows down to cross it, offering an opportunity to peer down if you're brave enough.

It's pretty impossible to shake off the feeling the monorail is hanging upside down when aboard this unusual train-like contraption. The Wuppertal Monorail is a suspended monorail, meaning it travels along a track above it, rather than below. Opened in 1901, it carries 85,000 passengers daily along its 20 stops peppered throughout the city in western Germany. It's particularly frightful when the carriages dangle above the river.

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Built by the British in the late 1800s, Sri Lanka's rail system was originally used to transport tea and coffee for export so it's no surprise that this seven-hour trip takes passengers through stunning tea plantations, remote villages, lush green hills and tumbling waterfalls. But traversing the mountainous landscape means the train connecting Kandy and Ella often chugs along steep cliffsides and across tall bridges that pass through the canopy. It's a heart-stirring trip, often dubbed the most beautiful in the world, but it's not without its chilling moments.

Travelling at an extreme altitude, the Qinghai–Tibet railway is the highest line in the world, extending between Golmud and Lhasa. Just five pairs of passenger trains run along these tracks as each has to be specially equipped for high elevation. For example, the locomotives are turbocharged to combat the effects of extreme altitude, the passenger carriages on Lhasa trains have an oxygen supply for each passenger and there's a doctor on every train. The line's highest point (and also the highest in the world that can be reached on a train) is the Tanggula Pass at 16,640 feet (5,071m) above sea level.

A journey on this train might not be across rickety bridges, over terrifying canyons or past steep mountainsides, yet there's something about this train that might make some quite uncomfortable. Travelling at a mind-boggling speed, Shanghai's maglev (magnetic levitation) train is the fastest passenger train in the world. Cruising at a spine-tingling 268mph (431km/h), the train connects Shanghai Pudong International Airport with Longyang Road Station in the outskirts of Pudong. At top speed, the 18-mile-long (29km) journey can be completed in just over seven minutes.

This simple wooden platform is a norry, or bamboo train, which runs on railway tracks. The original Cambodian bamboo train was built during the UN's peacekeeping operation during the early 1990s. Running on disused tracks from Battambang to the surrounding countryside, the improvised trains ran at a terrifying speed of 31mph (50km/h). Although the original tracks from Battambang were shut in 2017 to make way for a new railway link, today travellers can still experience this unusual mode of transport in the Banan temple area.

Unlike the rest of the trips on this list, the Maeklong Railway is more terrifying when you're not actually on the train. Built to distribute the catch caught in the Gulf of Thailand to the rest of the country, the tracks slice straight through a market which defiantly hasn't moved an inch. As soon as one of the eight trains passing through daily can be heard approaching, the vendors start pulling in the umbrellas and moving their produce to reveal a narrow passageway for the train to travel through. A similar track, known as Train Street in Hanoi, Vietnam was closed due to safety issues though Maeklong Railway Market remains open.

Also known as Gornergrat Bahn, this Swiss railway was the country's first electric rail railway and still is the highest open-air railway in Europe. Opened in 1898 as a link between ski resort town Zermatt and the summit of Gornergrat, it's a dramatic albeit short trip. In just 33 minutes, the train climbs nearly 5,000 feet (1,500m) over spine-tingling bridges, through galleries and tunnels and past forests, rocky ravines and waterfalls.

Crossing one of the country's most volcanically active landscapes, the Takamori Line travels in the shadow of Mount Aso. Always subject to tectonic activity, the line's most hair-raising point is the Tateno Bridge. Following the damage from severe earthquakes in 2016, the entire line was shut down. Later the same year a section of the line between Nakamatsu and Takamori resumed service, but there've been no trains crossing the scenic but terrifying bridge ever since.

Although no longer operational, this unique route was the last scheduled passenger steam train in South Africa and was once considered the world's most extreme railway. A three-hour journey, the Outeniqua Choo-Tjoe Train ran between George and Knysna and was famous for several risky crossings across Indian Ocean beaches. Its scariest point was the 118-foot (36m) high Kaaimans Bridge, but sadly floods severely damaged the tracks in 2006 and the train ceased operations in 2009.

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Completed in 1884, the Georgetown Loop Railroad was an engineering marvel that attracted visitors from all over, making it one of the state's first tourist attractions. Chugging through the Rocky Mountains, it's a scary ride as the train slowly navigates its way across four bridges over Clear Creek. The highest, Devil's Gate High Bridge, welcomes travellers with a terrifying 100-foot (30m) drop and the ominously slow speed at which the train passes here makes it an even scarier experience.