Go underground and you gain a whole new perspective on the world. From a sauna inside a former mine to wartime tunnels and rock-hewn temples, we've dug up the most interesting underground attractions across the globe.

The Swedes have long been known for their sauna culture, but this unlikely new attraction sees the relaxing practice brought to an unexpected location. At the Adventure Mine in Dalarna, central Sweden, you can journey into a disused mine 262 feet (80m) underground and bathe in the mine's crystal clear waters, before sweating it out in a traditional wooden sauna. It's also possible to do a 'Lady of the Mine sauna ritual' which includes elements to awaken the senses and get endorphins going.

The San Luis Obispo County stretch of the Californian coast is home to a world of arches, caves, grottos and rock gardens that are only accessible from the water. Visitors can explore their watery depths on an exhilarating three-hour excursion with Central Coast Kayaks – some of the caves run up to 30 feet (9m) deep. If you’re lucky you’ll spot seals, otters and dolphins as you paddle through the North Pacific

A cliff face in Maharashtra hides remarkably well-preserved murals, carvings and sculptures dating from the 1st or 2nd century to the 5th century, which are considered masterpieces of Buddhist religious art. Lost until a hunting party stumbled across an entrance in 1819, the 30 or so caves have a network of halls, with columns carved out of the rock.  

Just outside Reykjavík, you can walk through 100-foot-wide (30m) tunnel formed as a lava tube in a volcanic eruption more than 5,000 years ago. In some places the roof has caved in and natural light – and snow – floods in. Elsewhere, impressive lighting highlights the colours and geological formations.

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Originally a fortress and then a royal residence, today the Louvre holds one of the world’s finest collections of art and architect I.M. Pei’s glass pyramid has become an iconic Paris landmark. The once-controversial entrance to a huge underground lobby was initially deemed too modern by some, but today is synonymous with the French capital. There’s also a fascinating underground walkway past the medieval foundations of the Louvre.

Delve beneath the buzzing cafes of City Market in Indianapolis and you'll find an eerily quiet network of catacombs, stretching for 22,000 square feet (2,043sqm). The limestone brick arches and pillars were originally the basement of Tomlinson Hall, a vast municipal building that was demolished after a fire in 1958. After contruction work is finished around the markets sometime in 2025, organised tours will resume and give you the chance to explore the musty underground warren which is popular with ghost hunters.

There's plenty to explore beneath the surface of the world-famous Colosseum in Rome. Go underground to visit the dungeons where gladiators and animals waited before their fight. You can also see a reconstructed trapdoor and wooden elevator used to hoist fighters to arena level.

Visiting the stunning Drach Caves near Porto Christo in Mallorca is a truly magical experience. Visitors are ferried across a vast subterranean lake on wooden boats, through gorgeously lit caverns and under ceilings dripping with curtains of stalactite. Tours last roughly an hour and include a live classical music concert. A quartet of cellos, harpsichord and two violins have been serenading underground visitors in this most magical of venues since 1935.

This UNESCO salt mine in Poland has been mined since the 13th century. It's nine levels deep but only sections of the first three are open to the public – 1% of the entire mine. Chilly corridors lead to illuminated chambers with sculptures carved from salt and vast underground chapels. You can take individual or group tours.

Above ground, Antwerp is a fascinating mix of medieval history and contemporary cool. This unusual tour beneath its streets explores the network of sewers, vaults and canals in semi-darkness, while revealing the secrets of Belgium’s second city through the ages. Be prepared for bad smells...

St Paul’s in London is famous for its stunning dome, but what of the cathedral sights below ground? The crypt holds the tombs of the Duke of Wellington, Lord Nelson (pictured) and cathedral architect Sir Christopher Wren, plus many other ecclesiastical gems. The crypt and treasury are vast, running the entire length of the cathedral above. 

These caves near the border of Lesotho sit beneath one of the largest rock overhangs in the Southern Hemisphere. Motouleng means ‘the place where the drums keep beating’ in the local Basotho language and today the caves are considered a sacred site and a popular pilgrimage destination. Sangomas (shaman healers) live in the caves and perform spiritual healings, initiation rites and baptisms for pilgrims. You’ll also find traditional dwellings, drywalls and kraals made from straw and grass.

Wind Cave, deep below the South Dakota grasslands, is one of the world’s longest cave networks, where some of the rock formations date back 310 million years. It’s earned its name because when powerful winds blast in and out, the cave makes a whistling noise. Over 150 miles (241km) of its rocky passages have been explored and that's thought to only be 10% of the caves. The big draw is the boxwork, thin blades of calcite that project from cave walls and ceilings, creating intricate patterns.

Built by forced labour on the island of Guernsey during the Second World War, this military hospital doubled as a munitions store for occupying German forces. All that can be seen above ground are the small entrances and ventilation shafts, but underground there is around 75,000 square feet (6,950sqm) of tunnels you can explore.

Adventurers will love the four-hour Deep Darkness tour inside the lower caves at Indiana Caverns. It's physically challenging, starting with a descent down a 93-foot (28m) ladder followed by a section of scrambling over boulders and crawling through watery passages. The final part is a kayak down a subterranean river – keep your eye out for cave crayfish.

Port is at the heart of Porto. Portugal’s second city is the place where the fortified wine is aged in tanks or wooden barrels and then exported. A cellar tour in Porto is a must and there are dozens of options with guided tours and tastings.

This mesmerising dripstone cave in Sauerland was discovered back in 1907 and has been one of Germany’s most popular caves ever since.  Visitors follow a 1.12 mile (1.8km) path past impressive stalagmites and stalactites that look remarkably like cheese. Interestingly, a local ‘cave cheese’ is matured in the cave for three months, the optimal conditions enhancing its piquant flavour. You can sample it at the shop onsite and see for yourself.

Beneath Sondermarken park in central Copenhagen lies a cathedral-sized underground reservoir that was once filled with 16 million litres of drinking water. It's now part of the Frederiksberg Museums and a venue for contemporary art exhibitions and events. This fascinating space also has naturally forming stalactites and stalagmites.

Carved out of solid rock with a copper dome roof, Temppeliaukio is a popular attraction in the centre of Helsinki, Finland. On the inside, exposed rock lines the walls and the altar is made from granite. Natural light floods in through the skylights creating a beautiful sight. It’s a serene place – when it’s not crowded with tourists. The acoustics are outstanding and concerts and recitals are held here throughout the year, and you can take a guided tour.

Onondaga Cave is a subterranean world of spectacular stalactites and lofty stalagmites in Onondaga Cave State Park. The tours are less commercialised than some Missouri cave systems, but nonetheless fascinating. There's a flowing river and crystal-clear pool with lily pad-like calcite deposits resting gently on the surface.

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There's an incredible underwater restaurant in Kristiansand in southern Norway. Designed by award-winning architects Snøhetta, Under looks like a rock formation rising from the sea. Guests descend 18 feet (5.5m) underwater to a dining room with floor-to-ceiling windows looking out on the watery depths. 

Cerro Potosi (also known as Cerro Rico, or Rich Mountain) in southern Bolivia made the Spanish Empire vastly wealthy, but cost the lives of Indigenous people and African enslaved people. There's barely any silver left in these high altitude mines and today mostly only tin is mined, and conditions for workers haven't improved. If you choose to visit (it's an eye-opening experience) then go with an ethical and responsible tour company.

In Nevada’s Great Basin National Park, the Lehman Caves is a spectacular cave system, formed from millions of years of subterranean streams dissolving the limestone rock. During the Prohibition era, it was used as a secret speakeasy, but now the attraction is the thousands of delicate columns, hollow stalactites (known as soda straws) and needle-like crystals. Join a tour and look out for "cave popcorn", small lumps of calcite that look surprisingly like the cinema snack.

Not far from Colombia’s capital city of Bogota, the Zipaquira salt cathedral is around 590 feet (180m) underground in an abandoned salt mine. The underground area is beneath an original sanctuary carved out by miners – the current cathedral space only opened in 1995. It’s open to visitors all week except on some Sundays when Catholic services are held here, despite the sight not being an official church. 

The southern Tunisian Berber village of Matmata was the Star Wars filming location for Luke Skywalker's birthplace. Typical Berber 'troglodyte' homes are built by digging out a large pit (which becomes a central courtyard) and then carving outer subterranean rooms in the soft sandstone. Tourists can take an organised tour through reputable companies.

The catacombs are a labyrinth of gloomy galleries and passageways in a disused quarry beneath the streets of Paris. Here lie the bones of millions of Parisians, moved here from overflowing city graveyards in the 18th and 19th centuries, and arranged in decorative, high Romantic-style displays.

In 1928, deep inside Tennessee’s Lookout Mountain, a hidden 145-foot (44m) waterfall was discovered tumbling into a limestone cave. You can take an atmospheric after-dark lantern tour through cavern trails to see the waterfall. Listen out, you'll hear the mighty, thunderous falls before you see it.

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Rome’s Domus Aurea (Emperor Nero’s 'Golden House') is a palace on an unbelievable scale. Now underground, frescoes are visible in excavated rooms and VR goggles allow visitors to see it as it was – a place of excess with marble walls, gold leaf decoration and dazzling jewels. The grounds of the palace covered most of ancient Rome. Domus Aurea was built (and destroyed) before the Colosseum was constructed.

Mammoth Cave in Kentucky gained its name for a reason. With over 400 miles (644km) of mapped passages, it's the longest cave system in the world. You can explore 10 miles (16km) of tunnels by guided hikes and the formations are staggering – admire Frozen Niagara, which looks just like a waterfall sculpted out of rock. The caves are also home to albino shrimps, cave fish and several endangered bat species.

Above ground, winter temperatures in Montréal can plummet to -15°C (5°F) but there's something hidden below the surface. La ville souterraine (the underground city) comprises 14 miles (22.5km) of passages providing access to the Métro, ice skating rinks, major hotels, restaurants, shops and underground parking. It's decorated with chandeliers, modern art and Canada’s largest indoor water fountain.

Deep in the desert of the Australian outback, Coober Pedy is a peculiar town where its 2,000 or so residents have dug down to escape the searing heat (pictured is museum Faye's Underground Home). It’s only a town in the first place due to opal mining and now tourism plays an important part. There's an underground opal museum, a hotel, a campsite and even a Serbian church.  

More of Australia's beautiful outback towns here

Members of the Texas Highway Department stumbled across Inner Space Cavern in 1963, when drilling through rock to test if it could support an overpass. When their drill fell through the roof of the Discovery Cave, they realised they were above a vast subterranean network. Today, you can explore the chambers, with their sharp stalagmites, still pools and even coral (this was once the ocean floor) on daily tours.

Visit Waitomo Caves on New Zealand’s North Island and explore a series of sculpted tunnels with stalactites and stalagmites before a boat trip on inky Waitomo River. Inside the vast cathedral grotto, see the ghostly constellations created by thousands of glowworms. 

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Buried on the fringes of Shenandoah National Park in Virginia, Luray Caverns are on a staggering scale. The epic chambers have ceilings over 10 storeys high and crystalline pools, such as Dream Lake, which has a surface so glassy it mirrors the stalactites above. There’s also the legendary Great Stalacpipe Organ, which can play Beethoven's Moonlight Sonata by using rubber mallets to strike 37 stalactites of varying sizes.

A place of pilgrimage in the heart of Ethiopia, Lalibela has 11 rock-hewn churches from the 13th century that are inscribed on the UNESCO World Heritage List. The monolithic House of Saint George (Biete Ghiorgis), in the shape of a cross, is isolated from the rest but was similarly chiselled out and connected to catacombs.

Seek out hidden chambers, stunning stalactite caverns formed in the Ice Age and prehistoric dwellings within Britain’s biggest gorge, a 400-foot (122m) deep and three-mile (4.8km) long natural formation set within Somerset's scenic Mendip Hills. One of the most notable is Gough’s cave, where Cheddar Man was discovered in 1903 – the oldest complete skeleton ever found in Britain.

Underneath Nuremberg’s imposing Imperial Castle lies one of the most extraordinary sights in Germany: a labyrinth of underground cellars and passageways, carved out of sandstone, and used to brew and store beer for over 700 years. The cellars sit 65.6 feet (20m) underground, spread over several storeys and cover a combined area of 269,098 square feet (25,000sq m). Tours of the maze of cellars and corridors show where townsfolk sheltered during the Second World War and often end with a traditional Nuremberg red beer.

Ancient Petra in Jordan boasts the imposing temple of Al Khazneh (The Treasury), an ancient Arab tomb carved directly into a sandstone rockface. The six-column façade is famous the world over courtesy of 1989 movie Indiana Jones and the Last Crusade, but the interior is a colossal inner chamber and sanctuary.

Deep beneath Edinburgh's Old Town, the gloomy subterranean passages of Blair Street Underground vaults were only rediscovered in the 1980s. Mercat Tours has exclusive access and runs regular tours to regale spooked tourists with fascinating insights into a murky past of smugglers, murderers and body snatchers.

This geothermal spring in Utah is buried within a dome-shaped limestone rock. The crater, 10,000 years in the making, formed when melting snow on the Wasatch Mountains seeped deep within the ground. The earth’s interior heated the water and as it percolated upward, it picked up minerals which were then deposited on the surface. Part of the Homestead Resort, you can swim, snorkel and scuba dive in the blue, bath-like, 35°C (95°F) water.

Iceland is one of the most active volcanic regions in the world but Thrihnukagigur, which translates as Three Peaks, is dormant. Last time Thrihnukagigur erupted was more than 4,000 years ago and today it's possible to go inside the volcano. Following a hike across a lava field, six to seven people at a time are lowered slowly into the empty magma chamber – a spectacular space that would easily fit the Statue of Liberty.

The Greenbrier bunker in West Virginia was built in the late 1960s to safeguard the US Senate in the event of nuclear war. The top-secret project was designed to house 1,100 people, hidden beneath the West Virginia wing of the Greenbrier resort, behind 18-tonne blast-proof doors. The two-storey building has bedrooms kitted out with bunk beds, decontamination showers and its own power plant. Visitors are welcome on daily tours to explore the 153 rooms.

This secret, deserted world beneath Butte, in Montana, includes a barber shop, shoe shops, a prison and speakeasy. These are well-preserved relics from the early 20th century, when mining was at its height and there was prohibition. The population swelled to around 100,000 and space was at a premium, so people started using underground areas connected by tunnels. Today, you can visit them on a subterranean tour.

Now part of the Imperial War Museum in London, Churchill War Rooms were the underground headquarters below Westminster where Winston Churchill and his government sheltered during the Blitz. Many of the rooms have been left just as they were when the lights were switched off in 1945. The intriguing level of detail makes it easy to imagine the tense atmosphere when Churchill’s inner circle was planning wartime strategies.

A 45-minute drive from the bright lights of Vegas you’ll find the unspoiled Black Canyon. Join a guided kayak tour through the unusual rock formations and still waters of Emerald Cove. Its namesake cave is particularly breathtaking. The sun’s reflection off the surrounding cavern’s yellow-brown walls combined with blue from the sky, gives the water a vivid green appearance.

This spectacular sea cave on the uninhabited Isle of Staffa in Scotland's southern Hebrides has a striking appearance. Fingal’s Cave, with its neat hexagonal columns of basalt, is similar in appearance to a Gothic building, yet it isn’t man-made. You can walk overland to the cave's large arched entrance and explore the extraordinary formation up close. Alternatively take a boat trip to pass by the gaping mouth of the vast cavern.

Deep underground, beneath the mountains of southern Snowdonia, where mid-Wales meets North Wales, is a disused slate mine. Book onto a family-friendly tour where a cloaked boatman will lead guests past a waterfall, along winding tunnels and into vast underground caverns, all the while recounting Welsh myths and legends of King Arthur and wizard Merlin. The attraction reopens March 2022.

This rusty-red cavern is only four-foot wide and deep (1sqm), but its vibrant colour and otherworldly formations make it worth the visit. The sandstone rock has slowly been eroded by wind, forming the Windstone Arch and alien-like shapes. The attraction is hidden out of sight and could easily be overlooked, down a dirt track in Nevada’s Valley of Fire State Park. You don’t need a tour to visit, but will need the GPS coordinates.

Preserved remnants of the former Portuguese occupation of Moroccan port city Mazagan (El Jadida) can be found at this intriguing site. Although control ended in 1769, the fortification of the old town and the remarkable cistern beneath remain much as they were. The cistern was a filming location for Orson Welles’ Othello, and the shadows and reflections from the water make it a mysterious space to explore.

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These underground slate caves in North Wales have been re-created as an exciting subterranean playground. The brightly lit cavern holds six huge trampoline-style nets, the highest is at 180 foot (55m) – think cathedral spire kind of height – and there are chutes to drop between levels. 

Hamburg’s gorgeous Art-Deco St. Pauli Elbtunnel, now known as the Old Elbe Tunnel, was built in 1911 to provide a more direct route for dock workers making their way from southern banks of the Elbe river to Landungsbruecken piers in St. Pauli. The 1,498-foot -long (426m) arched tiled underpass sits 79 feet (24m) under the river surface and is lined with atmospheric lamps. After several new bridges were built in the 1970s, the Elbe Tunnel is used mainly by pedestrians and cyclists and is one of the most popular tourist attractions in the city.

Only discovered in 1868, this extraordinary cave in northern Spain is covered with prehistoric paintings of bison, deer and horses believed to be over 14,000 years old. Understandably, the cave has been closed to the public since 1977 for conservation reasons, but an exact replica has been created nearby for visitors to explore. This ‘Neo-cave’ mimics the original cave’s structure and artwork, with each painting painstakingly reproduced using the same techniques as the original artists.