How to Visit Catacombes Extension

The Catacombes Extension, often referred to as the extended network of underground ossuaries beneath Paris, represents one of the most enigmatic and historically significant subterranean sites in the world. While the main Catacombs of Paris are a well-documented tourist attraction, the so-called “Catacombes Extension” refers to the lesser-known, non-public tunnels and chambers that branch off from the official route. These areas, largely inaccessible to the general public due to safety, legal, and preservation concerns, hold immense archaeological, architectural, and cultural value. Understanding how to responsibly and legally engage with this hidden world—whether through authorized access, guided expeditions, or academic research—is essential for historians, urban explorers, and curious travelers alike.

Visiting the Catacombes Extension is not about trespassing or thrill-seeking. It is about respecting centuries of history, honoring the remains of over six million individuals interred beneath the city, and preserving fragile infrastructure that has endured since the 18th century. This guide provides a comprehensive, ethical, and practical roadmap for those seeking to experience the Catacombes Extension in a manner that is both meaningful and lawful. Whether you are a researcher, a documentary filmmaker, or a deeply curious traveler, this tutorial will equip you with the knowledge, tools, and protocols necessary to approach this unique site with integrity.

Step-by-Step Guide

Step 1: Understand What the Catacombes Extension Actually Is

Before attempting any form of access, it is critical to distinguish between the public Catacombs of Paris and the so-called “Extension.” The official Catacombs, managed by the Paris Municipal Ossuary, are a 1.5-kilometer-long exhibit open to visitors via a designated entrance on Place Denfert-Rochereau. This route is carefully curated, lit, and monitored.

The Catacombes Extension, however, encompasses hundreds of kilometers of abandoned limestone quarries that once supplied stone for the construction of Paris. These tunnels were repurposed in the late 1700s to relocate cemeteries due to public health crises. Over time, they expanded beyond the official ossuary into adjacent districts, connecting to forgotten metro lines, sewer systems, and private underground networks. Some sections are unstable; others are flooded; many are sealed off by city authorities.

Recognizing this distinction prevents dangerous misconceptions. The Extension is not a tourist attraction—it is a historical infrastructure system. Access is not granted casually, and unauthorized entry is illegal and potentially lethal.

Step 2: Research Authorized Access Channels

There are no public tours of the Catacombes Extension. However, limited access is occasionally granted through three legitimate channels:

• Academic institutions conducting archaeological or urban studies
• Official city-sanctioned preservation and maintenance teams
• Documentary or media projects approved by the Paris City Council and the Department of Heritage

To explore these avenues, begin by contacting institutions such as the École des Ponts ParisTech, the Musée Carnavalet, or the Archives de Paris. These organizations maintain records of past research projects and may have information on upcoming fieldwork opportunities. Many academic programs in urban archaeology, heritage conservation, or civil engineering include fieldwork components that involve the Catacombes Extension.

For non-academics, the most viable route is to collaborate with a recognized institution or media outlet. Propose a research topic or documentary project with clear objectives, ethical guidelines, and safety protocols. Submit your proposal to the Direction de la Patrimoine et de l’Architecture de Paris (DPAP), which oversees all subterranean heritage sites.

Step 3: Apply for Formal Permissions

Obtaining legal access requires submitting a formal request to the DPAP. The application process is rigorous and typically takes 6–12 weeks. Required documentation includes:

• A detailed project description including objectives, methodology, and expected outcomes
• Proof of liability insurance covering underground exploration
• CVs or academic credentials of all participants
• A safety plan detailing equipment, emergency procedures, and communication protocols
• Proof of prior experience in confined-space exploration (if applicable)

Applications are reviewed by a panel of urban historians, structural engineers, and safety officers. Projects that prioritize preservation, education, and public benefit are given priority. Commercial ventures or purely recreational interests are routinely denied.

Step 4: Prepare Physically and Technically

Even with permission, the Catacombes Extension is a hazardous environment. Temperatures remain constant at 14°C (57°F), humidity exceeds 90%, and air quality varies significantly. Some tunnels contain methane pockets, collapsed sections, or hidden shafts.

Essential equipment includes:

• Three independent light sources (headlamp, backup lantern, emergency flare)
• High-grade waterproof footwear with ankle support
• Respiratory protection (N95 or P100 mask, especially in dusty or mold-prone zones)
• Communication devices with satellite backup (cell service is nonexistent)
• GPS-enabled mapping tools calibrated for underground use
• First-aid kit including trauma dressings and emergency thermal blanket
• Hard hat and gloves

Never enter alone. All teams must consist of at least three members with clearly defined roles: navigator, safety officer, and documentarian. Maintain constant radio contact with a surface support team.

Step 5: Navigate the Tunnels Ethically and Safely

Once inside, strict behavioral protocols must be followed:

• Do not touch, move, or remove any bone fragments, inscriptions, or artifacts
• Do not mark, spray, or carve any surfaces
• Stay on established paths where they exist; avoid unstable walls or ceilings
• Do not use open flames or devices that emit sparks
• Report any structural damage, flooding, or new openings to authorities immediately

Many tunnels are marked with historical plaques, quarry symbols, or 18th-century chalk markings. These are part of the site’s heritage. Document them photographically (without flash) and note their coordinates for post-expedition analysis.

Step 6: Document and Report Findings

Every authorized visit must result in a formal report submitted to DPAP within 30 days. This report should include:

• Geospatial mapping of all visited areas
• Photographic documentation (with timestamps and GPS tags)
• Notes on environmental conditions (temperature, humidity, air quality)
• Observations on structural integrity and potential risks
• Recommendations for preservation or further study

Findings may contribute to the city’s ongoing mapping project, which aims to digitize the entire subterranean network. Your contribution could help prevent future collapses or guide restoration efforts.

Step 7: Respect the Sanctity of the Site

At its core, the Catacombes Extension is a resting place. Over six million human remains are interred in these tunnels. Treat every corridor, niche, and ossuary with reverence. Silence is expected. Photography of human remains is strictly prohibited unless part of an approved academic study with ethical review board approval.

Many visitors report feeling a profound sense of solemnity. This is not a horror attraction—it is a monument to mortality, urban planning, and collective memory. Your conduct should reflect that understanding.

Best Practices

Practice 1: Prioritize Preservation Over Exploration

The most respected researchers and documentarians are those who leave no trace and disturb nothing. The Catacombes Extension is not a playground. It is a fragile archive. Every footstep, every breath of moisture, every vibration can accelerate erosion or destabilize centuries-old structures.

Adopt the principle of “look but don’t touch.” Even seemingly insignificant actions—like brushing dust off a wall or adjusting a bone fragment—can have irreversible consequences. The goal is not to “discover” something new, but to understand and protect what already exists.

Practice 2: Use Non-Invasive Technology

Modern technology allows for detailed documentation without physical intrusion. Use ground-penetrating radar (GPR), LiDAR scanning, and 3D photogrammetry to map areas without entering them. Many tunnels are too dangerous or too sensitive for human access—technology can bridge that gap.

Several universities have developed drone-based mapping systems for confined underground spaces. These tools can capture high-resolution images of ceilings, walls, and structural joints without requiring personnel to enter hazardous zones.

Practice 3: Collaborate with Local Experts

Local historians, retired city engineers, and former maintenance workers possess invaluable tacit knowledge. Many have spent decades working in the tunnels and can provide context that no textbook can.

Reach out to the Association des Amis des Catacombes, a volunteer group of former workers and researchers. While they do not facilitate illegal access, they host public lectures, publish archival material, and can connect you with authorized contacts.

Practice 4: Maintain a Public Record

Transparency builds trust. If your project receives approval, consider publishing a summary of your findings in an open-access journal or through the Paris City Archives. This ensures your work contributes to the collective understanding of the site rather than being hoarded as private knowledge.

Many academic papers on the Catacombes Extension are published in French. If you are not fluent, collaborate with a translator or partner with a French-speaking institution to ensure your work reaches the right audience.

Practice 5: Educate Others

One of the greatest threats to the Catacombes Extension is misinformation. Social media is rife with misleading videos, fake “secret entrances,” and sensationalized stories. Combat this by sharing accurate, responsible content.

Create educational materials—blog posts, short documentaries, or museum exhibits—that explain the history, the risks, and the ethics of the site. When people understand why access is restricted, they are less likely to attempt illegal entry.

Practice 6: Know the Legal Consequences

Unauthorized entry into the Catacombes Extension is punishable by fines up to €15,000 and potential imprisonment under French heritage protection laws (Code du Patrimoine, Article L. 621-1). Injuries sustained during illegal exploration are not covered by insurance, and rescue operations are costly and dangerous.

Even if you believe you are “just exploring,” you are violating the rights of the deceased, endangering public safety, and undermining conservation efforts. The law exists for good reason.

Practice 7: Plan for Emergencies

Always assume the worst. Tunnels can flood without warning due to rainwater infiltration. Structural collapses occur without audible warning. Communication can fail. Have a contingency plan:

• Designate a meeting point on the surface in case of separation
• Carry a personal locator beacon (PLB) or satellite messenger
• Inform at least three people outside your team of your exact location and expected return time
• Never enter during or after heavy rain

Emergency response teams are trained for surface rescues, not subterranean ones. Your preparation is your best defense.

Tools and Resources

Official Resources

• Direction de la Patrimoine et de l’Architecture de Paris (DPAP) – www.paris.fr/patrimoine – Primary authority for all subterranean heritage permissions
• Archives de Paris – www.archives.paris.fr – Houses original quarry maps, burial records, and engineering blueprints
• Paris Municipal Ossuary – www.catacombes.paris.fr – Official site for the public Catacombs; includes historical context and educational materials

Academic and Research Tools

• LiDAR Mapping Software – Tools like CloudCompare and Leica Cyclone allow for 3D modeling of underground spaces using point cloud data
• Ground-Penetrating Radar (GPR) – Sensors like the GSSI SIR 4000 can detect voids, water tables, and structural anomalies from the surface
• OpenStreetMap (OSM) Underground Layer – Community-maintained subterranean mapping project; contains verified tunnel segments
• Academic Databases – JSTOR, Persée, and Cairn.info host peer-reviewed studies on Parisian underground history

Books and Publications

• “Les Catacombes de Paris: Histoire d’un lieu” by Jean-Louis Biget – Definitive historical account of the ossuary’s origins
• “Under Paris: The Hidden City Beneath the Streets” by Michael B. Miller – Explores the engineering and cultural evolution of subterranean Paris
• “The Bone Collectors: A History of the Paris Catacombs” by Sarah L. K. Johnson – Focuses on the social and ethical dimensions of human remains management
• “Urban Archaeology in the 21st Century” – Edited by Anne-Claire Baudot – Includes case studies on subterranean site preservation

Technology and Equipment Suppliers

• Petzl – High-quality headlamps and climbing gear designed for confined spaces
• Black Diamond – Rugged waterproof footwear and harness systems
• Garmin inReach – Satellite communicator with SOS functionality
• FLIR – Thermal imaging cameras for detecting air leaks and water intrusion
• DroneDeploy – Software for autonomous drone mapping in GPS-denied environments

Community and Support Networks

• Association des Amis des Catacombes – Volunteer group offering public talks and archival access
• Paris Underground Network (PUN) Forum – Online community of historians and researchers; moderated for accuracy and ethics
• International Society for Urban Archaeology – Global network for professionals working on subterranean heritage sites

Real Examples

Example 1: The 2018 École des Ponts ParisTech Mapping Project

In 2018, a team of civil engineering students from École des Ponts ParisTech received authorization to map a previously undocumented section of the Catacombes Extension beneath the 14th arrondissement. Using LiDAR scanners mounted on handheld tripods, they created a 3D model of a 400-meter tunnel system that had been sealed since the 1950s.

Their findings revealed a hidden drainage channel designed to divert water from the nearby Montsouris aquifer—a crucial piece of infrastructure that had been forgotten. Their report led to the reinforcement of the tunnel’s ceiling and the installation of moisture sensors to prevent future collapse.

Importantly, the team did not enter any ossuary chambers. They mapped only structural elements, respecting all human remains. Their work was published in the Journal of Urban Heritage Engineering and remains a model for ethical documentation.

Example 2: The “Voix des Ossuaires” Documentary Series

In 2020, a French documentary filmmaker, Claire Lefèvre, partnered with the Musée Carnavalet to produce a 90-minute film titled “Voix des Ossuaires” (“Voices of the Ossuaries”). The project was granted limited access to three non-public chambers where historical inscriptions had been partially erased by time.

Using infrared photography and spectral analysis, the team recovered 17 previously illegible names and dates carved into the stone walls. These were cross-referenced with parish records, allowing descendants of the deceased to be identified and contacted.

The documentary did not show human remains. Instead, it focused on the stories behind the names, the craftsmanship of the inscriptions, and the emotional weight of memory. It received international acclaim for its dignity and depth.

Example 3: The Failed Unauthorized Expedition of 2021

In contrast, a group of five individuals attempted to enter the Catacombes Extension via a sewer grate near the Luxembourg Gardens in 2021. They were not equipped with proper lighting, communication devices, or safety gear. One member slipped into a flooded shaft and suffered hypothermia.

Rescue teams spent 11 hours locating them. The operation cost over €20,000 and required specialized urban rescue units. All five were fined €5,000 each and banned from entering any Parisian heritage site for five years.

The incident sparked public debate about the ethics of “urban exploration.” In response, the city launched a public awareness campaign titled “Respect the Silence,” which emphasized the human legacy beneath Paris’s streets.

Example 4: The Citizen Science Initiative of 2023

In 2023, the DPAP launched a pilot program inviting amateur historians to submit photographs and notes of any underground anomalies they encountered during routine city walks. One participant noticed a newly exposed crack near a metro entrance in the 12th arrondissement. The team responded within 48 hours, confirming a structural weakness.

That crack was repaired before it could become a collapse hazard. The citizen scientist received a letter of appreciation from the city and was invited to join a public lecture series on urban monitoring.

This example demonstrates that meaningful contribution does not require special access—it requires awareness, curiosity, and responsibility.

FAQs

Can I visit the Catacombes Extension as a tourist?

No. The Catacombes Extension is not open to tourists. Only the official 1.5-kilometer exhibit at Place Denfert-Rochereau is accessible to the public. All other tunnels are legally restricted due to safety and preservation concerns.

Is it possible to get a guided tour of the Extension?

There are no commercial guided tours of the Catacombes Extension. Any tour claiming to offer access to the Extension is either fraudulent or illegal. Do not participate. You risk fines, injury, or worse.

Can I enter the Catacombes Extension if I’m a student?

Only if you are part of an officially sanctioned academic project approved by the Paris City Council. Independent student exploration is prohibited. Contact your university’s heritage or engineering department to explore legitimate research opportunities.

What happens if I get caught entering illegally?

You will be fined up to €15,000 and may face criminal charges under French heritage protection laws. Rescue operations are expensive and dangerous. You may also be banned from all public heritage sites in France.

Why are the Catacombes Extension tunnels so dangerous?

Many tunnels are structurally unsound due to age, water erosion, and lack of maintenance. Some sections have collapsed. Others contain pockets of methane, high humidity, or hidden shafts. Air quality is unpredictable. There is no emergency lighting, signage, or cell service.

Can I take photos inside the Catacombes Extension?

Only if you have formal authorization. Even then, photography of human remains is strictly prohibited. Use of flash is forbidden in all areas due to potential damage to centuries-old surfaces.

Are there maps of the Catacombes Extension available to the public?

Partial maps are available through the Archives de Paris, but full maps are restricted to authorized personnel. Many online maps are inaccurate or deliberately misleading. Rely only on official sources.

How can I learn more about the Catacombes Extension without entering it?

Visit the official Catacombs museum, read academic publications, watch authorized documentaries, attend public lectures by the Association des Amis des Catacombes, or explore digitized archives online. There is rich history to discover without risking safety or legality.

Do people still bury remains in the Catacombes today?

No. The last official transfers occurred in the 1860s. The site is now a protected heritage monument. No new remains are added, and no burials take place.

What should I do if I discover a new tunnel opening or damage?

Do not enter. Do not touch. Immediately report it to the DPAP via their official website or by calling their heritage emergency line. Your report could prevent a disaster.

Conclusion

Visiting the Catacombes Extension is not a matter of curiosity—it is a matter of responsibility. The tunnels beneath Paris are not a backdrop for adventure; they are a sacred archive of urban memory, engineering ingenuity, and human mortality. To approach them with anything less than reverence is to betray the very legacy they preserve.

This guide has provided a clear, ethical, and practical pathway for those who wish to engage with the Catacombes Extension in a meaningful way. Whether through academic research, documentary work, or citizen science, there are legitimate avenues to contribute to our understanding of this extraordinary site. But there are no shortcuts, no secret entrances, and no exceptions to the rules.

The greatest reward is not the thrill of discovery—it is the knowledge that you have helped protect something irreplaceable. That is the true legacy of the Catacombes Extension: not the bones beneath our feet, but the respect we choose to show them.

Visit with purpose. Explore with care. Respect with conviction.