The secret world under our feet contains centuries of history, intrigue, and engineering feats that few tourists ever experience. Underground systems were once used as military bunkers, escape tunnels, storage rooms, and even housing during war.
These underground tunnels provide a glimpse into the past that you won’t experience in typical museums or tourist sites. Below is a list of 20 secret European underground tunnels open to tourists.
Every tunnel has a fascinating history.
Postojna Cave System – Slovenia
Slovenia’s Postojna Cave stretches for nearly 15 miles beneath the karst landscape, making it one of Europe’s largest cave systems. Visitors can ride an electric train through massive chambers adorned with spectacular stalactites and stalagmites formed over millions of years.
The cave is also home to the olm, an unusual aquatic salamander known locally as the ‘human fish’ due to its pinkish skin color.
Paris Catacombs – France
The Paris Catacombs contain the remains of more than six million people who were transferred from overcrowded cemeteries in the late 18th century. Visitors navigate through narrow passageways lined with carefully arranged human bones and skulls, which create elaborate wall decorations and memento mori displays.
The official tour covers only one mile of the extensive network, while the entire underground system spans over 200 miles beneath the city.
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Wieliczka Salt Mine – Poland
Poland’s Wieliczka Salt Mine features magnificent chambers carved entirely from salt, including an underground chapel with chandeliers made from salt crystals. Miners working in the depths created impressive sculptures and reliefs in the salt walls during their spare time over the centuries.
The mine reaches a depth of 1,073 feet and contains nearly 200 miles of tunnels, with tourists able to explore a 2-mile route featuring underground lakes and chambers.
Edinburgh Vaults – Scotland
Edinburgh’s South Bridge Vaults consist of 19 arches built in the late 18th century, creating cavernous spaces beneath the city streets. These chambers initially housed taverns and workshops but eventually became home to the city’s poorest residents, who lived in deplorable conditions.
Today, visitors can take guided tours exploring the dark history of these spaces, including tales of body snatchers, illegal whisky production, and reported paranormal activity.
Napoli Sotterranea – Italy
Naples sits above a vast honeycomb of tunnels and chambers carved from the soft volcanic tufa stone beneath the city. The Greeks built these passages as aqueducts, and the Romans expanded them.
During World War II, these passages were used as air raid shelters. Tour guides lead visitors through narrow passageways by candlelight, revealing ancient Greek-Roman cisterns, gardens, and even the remains of a Roman theater.
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Templars’ Tunnel – Portugal
The Templars’ Tunnel in Tomar, Portugal, connects the Convent of Christ to the Nabão River and serves as a secret passageway for the Knights Templar. Built in the 12th century, this underground corridor allowed knights to access water and escape routes without being detected during potential sieges.
Today, visitors can walk through the atmospheric tunnel and imagine the armored knights who once used these passages for both practical purposes and ceremonial processions.
Belchite Underground – Spain
The Spanish Civil War left behind a network of tunnels beneath Belchite, a ghost town preserved as a memorial to the conflict. Residents used these underground passages to escape bombing raids and move between buildings without being detected by enemy forces.
The tunnels still contain artifacts from the war, including discarded ammunition, personal items, and graffiti left by those seeking shelter below ground.
Basilica Cistern – Turkey
Istanbul’s Basilica Cistern was built in the 6th century, during the reign of Byzantine Emperor Justinian I, to store fresh water for the Great Palace. Three hundred thirty-six marble columns support the massive underground chamber, many salvaged from earlier Roman structures.
The columns create a forest of pillars reflected in the still water below. Two unusual Medusa head sculptures serve as column bases, positioned upside-down and sideways, supposedly to negate the mythological power of her gaze.
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Vienna Sewers – Austria
Vienna’s extensive sewer system gained worldwide fame through the film The Third Man, which showcased its brick-lined tunnels large enough for people to navigate. Built in the late 19th century following the model of Paris sewers, these underground channels helped transform Vienna into a modern metropolis.
Tours allow visitors to explore sections of this engineering marvel while learning about its history, construction, and role in urban development.
Orvieto Underground – Italy
Beneath the hilltop town of Orvieto lies a complex network of over 1,200 caves and tunnels carved by residents over nearly 3,000 years. Etruscan in origin, these spaces were later expanded by medieval and Renaissance residents seeking additional storage and workshop areas beyond the city walls.
Visitors can explore olive oil mills, quarries, and wells, including the remarkable Pozzo di San Patrizio, a double-helix well designed to ensure water access during sieges.
Bock Casemates – Luxembourg
Luxembourg City’s Bock Casemates form part of the ‘Gibraltar of the North,’ with 11 miles of underground tunnels carved into the cliff face. During wartime, these defensive passages could house thousands of soldiers, equipment, kitchens, bakeries, and workshops.
Though partially demolished after Luxembourg’s neutrality was established in 1867, the remaining sections offer visitors a glimpse into the city’s strategic military importance.
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Labirint at Buda Castle – Hungary
Budapest’s Buda Castle sits above a labyrinth of tunnels used throughout history for purposes ranging from military defense to wine storage and even as a prison. The cave system’s most infamous inhabitant was Vlad Tepes (the historical figure associated with the Dracula legend), who was imprisoned here in the 15th century.
The temperature remains a constant 59°F year-round, making it a refreshing escape during Budapest’s hot summers.
Chislehurst Caves – England
England’s Chislehurst Caves extend for 22 miles beneath the southeastern suburbs of London, formed from centuries of chalk and flint mining. During World War II, these tunnels served as an air raid shelter for up to 15,000 people, complete with a hospital, cinema, and chapel carved into the chalk walls.
The caves have also been used as a mushroom farm, a concert venue for bands like Led Zeppelin and Pink Floyd, and even as filming locations for episodes of Doctor Who.
Pilsen Historical Underground – Czech Republic
The Pilsen underground network stretches nearly 12 miles beneath the city center, representing one of Central Europe’s largest historical underground systems. Created between the 13th and 19th centuries, these passages served as food storage, water management systems, and emergency escape routes during the war.
The tour reveals medieval wells, ice cellars, and water wheels still preserved in their original state.
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Zonnebeke Church Dugouts – Belgium
British soldiers created Belgium’s Zonnebeke Church Dugouts around Ypres during the brutal trench warfare of World War I. These underground chambers housed headquarters, dressing stations, and sleeping quarters for troops seeking protection from relentless artillery bombardment.
The restored tunnels provide a sobering glimpse into the daily reality of soldiers who lived below ground for weeks, with original graffiti and artifacts still visible on the walls.
Galleries of Rabat – Malta
Malta’s capital city, Rabat, contains an extensive network of early Christian catacombs dating back to the 3rd century. These underground burial chambers feature remarkable frescoes, carved stone tables for memorial meals, and distinct sections for different religious communities.
The complex layout suggests the tunnels also served as hiding places during persecution before Christianity became accepted.
War Tunnels of Vianden – Luxembourg
Vianden Castle in Luxembourg sits above a network of defensive tunnels designed to protect the medieval fortress from attack. Engineers carved these passages through solid rock, creating arrow slits for defenders and access routes to allow soldiers to move between strategic positions quickly.
The tunnels included secret chambers where castle residents could hide valuable possessions during times of siege.
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Odessa Catacombs – Ukraine
Ukraine’s Odessa Catacombs form the world’s largest urban tunnel system, with estimates suggesting over 1,550 miles of passageways beneath the city. Originally limestone mines, these tunnels later housed Soviet partisans fighting against Nazi occupation during World War II.
Only a small portion is open to the public, as the vast majority remain unmapped and potentially dangerous to explore without professional guidance.
Kiek in de Kök Tunnels – Estonia
Tallinn’s Kiek in de Kök museum includes access to a network of 17th-century tunnels built beneath the Swedish bastions. These passages, known as bastion tunnels, were designed to allow troops and equipment to move between defensive positions without being exposed to enemy fire.
The tunnels later served as bomb shelters during World War II and now feature exhibits about their various uses throughout Estonia’s complex history.
Quinta da Regaleira Initiation Well – Portugal
The Quinta da Regaleira estate in Sintra features an unusual ‘inverted tower’ that spirals 88 feet into the earth. This mysterious structure, the Initiation Well, was created for ceremonial purposes related to Masonic rituals and Tarot symbolism.
A series of underground tunnels connect the well to other locations on the estate, including grottos, lakes, and fountains, all laden with esoteric symbolism.
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Underground Heritage
The extensive tunnel system under the surface of Europe shows how past generations have built spaces for shelter, storage, prayer, and survival. From Roman aqueducts to World War II bunkers, these underground worlds have stories that the buildings above cannot tell.
Whether you’re interested in the engineering feats, the history, or the excitement of seeing places that are not visible to the naked eye, these underground locations provide an alternative view of European history below the surface of more conventional tourist activities.
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