From the (Under)ground Up: A New Vision for the Notre Dame Cathedral

By Luke Carothers

During its more than eight centuries, the Notre Dame Cathedral in Paris has seen, hosted, and survived more than its fair share of historical events and disasters.  Perhaps most harrowing of these was the fire that engulfed the cathedral’s roof and spire in April of 2019.  By the time the blaze was controlled, Notre Dame’s famous spire had collapsed, most of the roof was destroyed, and there was extensive damage to the upper portions of the structure’s walls.

Images of this cultural icon burning elicited an outpouring of grief from around the world, which quickly reverberated as shockwaves of support and aid.  One of the most prominent examples of this aid came from the AEC industry as rebuilding efforts began immediately following the fire.  Led by its CEO Andrew Anagnost and Vice President of AEC strategy Nicolas Mangon, Autodesk aided in the rebuilding efforts by using their technology to create a 3D BIM model of Notre Dame Cathedral before the fire.

With tools provided by Autodesk, the process of cleaning and scanning the structure began.  During this time, Autodesk continued to support the teams working on the structure–offering tools and advisors to anyone working on the project.  This period of the restoration process lasted nearly three years, with the modeling sequence and cleanup efforts being completed in the Fall of 2022.  Using this BIM model, the teams working to restore the structure to its previous state are better equipped to manage construction sequences and logistics as well as calculate fluid dynamics for stability.

While the structure is being restored to its former self, its immediate surroundings will be updated to support its continued operations in the modern era.  Running parallel with the restoration efforts, the City of Paris launched a design competition in 2021 to reimagine the urban landscape surrounding the cathedral.  The project site includes the forecourt of the cathedral and its underground space as well as areas over the bank of the Seine River.  The immediate surroundings of Notre Dame constitute one of the most heavily trafficked areas in the world.  Largely untouched for centuries, this area now creates problems for its modern usage, resulting in things such as traffic and congestion.  With cleanup and scanning taking place and the outbreak of Covid-19 in 2020, the lack of visitor traffic in the area provided a good opportunity to re-envision what the space could be.  

Four international multidisciplinary teams–led by architects, urban planners, and landscape architects–were invited to submit their design proposals.  Autodesk was the technology partner for the competition, providing technological expertise throughout the competition.  Autodesk’s BIM solutions were used to create a 3D model of the existing area surrounding the cathedral.  This model allowed the teams to understand the unique constraints of the site.  The teams again utilized Autodesk’s BIM technology and advisors to create photorealistic visualizations of their design proposals.  Furthermore, the digital documents produced during the competition were available to the four teams, the City of Paris, and Autodesk, which allowed them to collaborate in real time on the Autodesk Construction Cloud platform.

In June of 2022, the City of Paris announced that the team led by Bureau Bas Smets was selected as the winner of the design competition.  Led by landscape architect Bas Smets, urban planners GRAU, and heritage collaborators Neufville-Gayet, the winning design is extensive–reimagining the square and underground parking spaces beneath it.  This reimagining also includes the archeological crypt, the Jean XXIII square located behind Notre Dame, the riverbanks, and some adjacent streets.  

A major part of this redesign focuses on the areas below the cathedral’s forecourt.  Under the forecourt is a large parking structure that was built in the 1970s, which has fallen out of use.  The winning design by Bureau Bas Smets seeks to breathe life into this space by turning it into a reception area for visitors to the cathedral.  This new design creates a passageway with an area of 3,170 meters for such a purpose.  To create this passageway, alterations will be made to the parking structure such as the removal of the immediate ceiling, which will create a four meter high and 60 meter long entrance hall for the cathedral.  Furthermore, the parking structure’s concrete pillars–which will flank this new entrance hallway– will be sandblasted to create a more aesthetic surface finish.  Along with creating a welcome center better adapted to host visitors in the modern age, this new plan for the areas underneath Notre Dame’s forecourt also connects these visitors with two other important areas: the Crypt of Notre Dame and the river Seine.

Opened to the public in the 1980s, the crypts beneath Notre Dame Cathedral house several important archeological discoveries that pre-date the building of the cathedral and even the city of Paris itself.  Over the years, researchers have found the remains of a Gallo-Roman docking port and public bath,  stretch of fourth-century ramparts, and parts of a medieval road and church.  Despite this wealth of archeological history, the crypts beneath Notre Dame are vastly under-visited when compared to the structure above.  A large part of this is due to the entrance to the space being offsite since its opening.  The new plan for the space under Notre Dame cathedral is set to change this and elevate this historical site to the forefront.  The new entrance space envisioned by the Bureau Bas Smets team will feature a new entrance to the crypts, adjacent to the entrance to the cathedral.

This new onsite entrance to the crypts below Notre Dame is one of the key ways this new vision for the area will create stronger links between the future and the past.  Another major way this project will connect the future and the past is by including the river Seine.  The history of Notre Dame and the Seine are inextricably linked, and this new design pays tribute to this connection.  Along with providing entrances to the cathedral and crypts, the new underground space will also open onto the Seine via a new opening in the quay wall.  Using tools provided by Autodesk, the winning design team was able to test and model design options for their concept.

Work on the winning project is expected to begin in 2024 and complete in 2028.  When the project is complete and restorations are finished, the Notre Dame Cathedral will be entering into a new era of its history.  When images of Notre Dame burning filled television screens around the world in 2019, the world held its breath and braced for loss.  However, with an outpouring of support from around the world–and the tools and expertise of the AEC industry–this iconic structure is not only going to be restored.  Rather, the Notre Dame Cathedral will be renovated in such a way that builds on its unparalleled past.  In doing so, this new vision for the world icon is able to strike a fine balance between the past and modernity.

Luke Carothers is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at lcarothers@zweiggroup.com.