Waitomo Caves, New Zealand

Waitomo sits on a veritable Swiss cheese of limestone, with deep sinkholes and beautifully sculpted tunnels all lit up by ghostly constellations of glow worms. As you ride in a dinghy across an inky underground lake the green pinpricks above your head resemble the heavens of some parallel universe.

Coober Pedy, Australia

In the virtually waterless outback, in searing temperatures and extreme terrain, the underground people of this town have created the “opal capital of the world”. The name Coober Pedy stems from an Aboriginal phrase meaning “white man’s burrow” and here homes, museums, opal shops and even art galleries all exist beneath the surface.

Cango Caves, South Africa

A quarter of a million visitors come to Oudtshoorn each year to gasp at the fantastic cavernous spaces, dripping rocks and towering columns of calcite in the Cango Caves. The awesome formations here are the work of water constantly percolating through rock and dissolving limestone on the way.

La Ville Souterraine, Canada

Winter in Canada is extreme and canny Montréalers have created the largest underground city in the world in order to avoid the cold. Since the 1960s, 33km of connected passages have spread to provide access to the Métro, major hotels, shopping malls, thousands of offices, apartments and restaurants and a good smattering of cinemas and theatres.

Craters of the Moon National Monument, USA

This surreal 83-square-mile park in southern Idaho arose from successive waves of lava pouring from wounds in the earth’s crust for over a millennium. The caves are damp, pitch black and silent, but where rocks have collapsed bright sunlight floods in to reveal the secrets of the underground.

City Hall Station, USA

This New York City subway station opened to great fanfare in 1904 but is today eerily silent. The architectural grandeur of the disused station – stained glass windows, skylights and brass chandeliers adorn its curved walls and arched ceilings – can only be viewed by passengers as train #6 loops back uptown or at occasional events like this Centennial celebration.

Yucatan’s cenotes, Mexico

The limestone shelf that forms the Yucatan Peninsula is riddled with sinkholes called cenotes. The most stunning are enormous deep wells of turquoise water set in dramatic caverns and considered by the Maya to be gateways to the underworld.

Puerto Princesa Underground River, Phillippines

A guided boat tour beneath low-lying limestone cliffs and through vast unlit sepulchral chambers is an unforgettable and magical experience. This unique underwater river system is said to be the longest in the world and is visited by more than five hundred thousand tourists each year.

Reed Flute Cave, China

Named for the reeds once found outside the entrance, this natural limestone cave is a brightly lit magical fairyland with impressive stalactites, stalagmites and rock formations. This reflective pool in the heart of the cave makes for a breathtaking spectacle.

Mary King’s Close, Scotland

Spooky tours led by costumed actors explore the warren of underground streets and spaces beneath Edinburgh’s Royal Mile. Tenements had been built on the steep hillside and when work on the City Chambers began in 1753, the tops of existing houses were simply sliced through and the new building constructed on top.

Ajanta Caves, India

Hewn from the near-vertical sides of a horseshoe-shaped ravine, the caves at Ajanta occupy a site worthy of the spectacular ancient art they contain. The remarkably preserved murals, carvings and sculpture dating from 200 BC to 650 AD are considered masterpieces of Buddhist religious art.

Derinkuyu Underground City, Turkey

Located in a rain-washed basin in Southern Cappadocia, this extensive ancient underground city contains family rooms, communal areas, stables, churches, wine and oil presses, chimneys to bring fresh air, wells to bring fresh water, a school complete with study rooms, and even makeshift tombs. Thousands of people could retreat behind stone doors to safety.

Catacombs of Paris, France

Tourists can wander through miles of claustrophobic, dark and damp caves, tunnels and quarries said to hold the bones of around six million Parisians. Lining the gloomy passageways, long thigh bones are stacked end-on, forming a wall to keep in the smaller bones and shards, which can be seen in dusty, higgledy-piggledy heaps behind.

Cheddar Caves, England

Beneath the towering Cheddar Gorge in the southwest of England, the Cheddar Caves were scooped out by underground rivers in the wake of the Ice Age. Today the vast caverns are floodlit so that visitors can gaze upon beautiful stalagmites, stalactites and rock formations mirrored in glassy pools.

Kverkfjöll Glacier Caves, Iceland

Lurking beneath Iceland’s stark interior is a frighteningly active volcano whose intense heat melts ice from the base of the glacier. The tunnels and caverns etched by the rivers are enthralling frozen palaces that stretch for over 2km and are best explored with an experienced guide.

Capuchin Ossuary, Italy

This macabre attraction beneath the Church of Santa Maria della Concezione in Rome displays the bones of more than 4,000 friars who died between 1500 and 1870 in elaborate and ornamental designs along the walls.

Casemates du Bock, Luxembourg

Beneath the northeastern corner of Luxembourg City’s old historic district, the vast network of underground passages and chambers here are a clear legacy of the country’s strategic position within Europe. Now a World Heritage Site, what remains of the underground ramparts is eerie, claustrophobic and utterly fascinating.

Grotto di Nettuno, Sardinia

Reached either by boat or by 656 vertiginous steps carved into the face of the cliff, these stunning natural caves became a popular tourist attraction after being discovered by fishermen in the eighteenth century. Stalactite and stalagmite formations and a saltwater lake are highlights inside.

Wieliczka Salt Mine, Poland

Placed on the original UNESCO World Heritage list in 1978, this astounding underground mine not far from Kraków is visited by more than one million tourists each year. Nine levels have more than 300km of galleries with works of art, altars, and historic and religious figures sculpted in the salt.

Grotte de Pech Merle, France

Original prehistoric cave paintings can be viewed close to the village of Cabrerets in southwest France. The astonishing rock art depicting bison and mammoths was discovered in 1922 and short of inventing a time machine, this is the closest you’ll get to the mind of Stone Age man.

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