• Genesis of the project
• Continuity and porosity, the two guiding principles of the project
• A project with three areas of focus: arts, events, and sports
• Focus on the pilot project

Historically, the Paris La Défense slab was designed to separate the functions intended for users of the district from those intended for technical or logistical purposes. However, several tens of thousands of square meters of basement space remain unused, representing:

• 350 m long,
• 13 to 70 m wide,
• 110,000 m3,
• Heights varying between 2.5 and 12 m.

Paris La Défense has decided to launch a competitive dialogue with international architects to imagine what will become of the 20,000 m² located under the esplanade, including the iconic “Cathedral” space of over 5,000 m², with the aim of creating new unique living spaces on a scale that will be unmatched in the Île-de-France region.

The proposal by Belgian architecture firm Baukunst was selected in March 2020. It will be implemented gradually, both in terms of time and space. Although the project has been designed as a whole, the complexity of the infrastructure means that it must be carried out step by step.

The four spaces involved in the final project are as follows: The Cathedral: 5,000 m² / Ceiling height (HSP): 6 m to 11 m The Moretti Workshop: 2,240 m² / HSP: 4 m to 12 m The FNAC: 4,480 m² / CH: 2.5 m to 10 m The Bassins: 4,600 m² / CH: 7 m

Baukunst has designed the project around two main areas of focus:

• creating continuity between the various spaces that are currently compartmentalized,
• optimizing connections between the slab and the lower levels.

The implementation of these principles involves two major achievements within the framework of the project:

• a public promenade reminiscent of Parisian passages. The backbone of the project, this path will distribute the successive volumes and connect to the Place Basse,
• a monumental footbridge in the shape of a ring “floating” above the Place de la Statue. As the main entrance to the buildings, it will be accompanied by high-quality landscaping. Interior gardens will be connected to the green spaces of the slab by shafts that let in natural light, like a patio. An oculus will allow pedestrians on the Esplanade to observe the activity in the spaces below, and more specifically to enjoy a view of Le Monstre, a work by artist Raymond Moretti.

The interventions will aim to open up spaces and maximize potential connections, in the medium and long term, with other existing infrastructure such as Cœur Transport, the Parking Centre Grande Arche, and the Voie des Sculpteurs.

The originality of the Baukunst agency's project lies in its ability to reveal the potential of these forgotten spaces while allowing them to be constantly reinvented. This explains why the programming of the volumes is not fixed, even if certain perspectives are emerging. A unique vestige of life in the basements of La Défense in the second half of the 20th century, Le Monstre, a work by Raymond Moretti housed in his studio, foreshadowed the valorization of residual volumes. The artistic dimension appears to be a major focus in the staging of the site. A large venue for events and artistic expression will preserve Raymond Moretti's work and make it visible to all.

Paris La Défense is currently studying a mixed program that should be open to leisure activities, with restaurants and wellness facilities, as well as events and sports.

The volumes will take the form of an architectural promenade, punctuated by plays of light and shadow and artistic and event-based experiences.

The interior life of the spaces will be signaled by the Ring, the Agam Pavilion, and the project's technical features, giving a new dimension to the composite landscape of the slab. A promenade will wind its way from one site to another, providing access to the impressive spaces of the Cathedral and the Moretti Workshop, where the Monster seems to await its visitors.

• Dominating the square, the Ring is both the symbol of the project and the main access point to the “forgotten spaces” of Paris La Défense. It will provide access to the site and allow natural light to enter the Cathedral. From this belvedere, pedestrians will be able to take an elevator, a monumental staircase, and a double escalator.

• Punctuated by landscaped rooms in contact with the surface, the underground walkway will wind its way through the heart of the infrastructure to a temporary staircase. A preview of a more complete walk between Place de la Statue and Cœur Transport, it will allow visitors to discover the memory and spirit of the place from the pilot phase onwards.
• Visible from the walkway and accessible via an exit, the Monster's Cellar and the Workshop will reveal the imagination of a neighborhood that is rediscovering itself. Their role will be particularly important in the preliminary phase to guide the programming of future concessionaires.
• In the long term, the underground walkway will wind its way through the heart of the infrastructure connecting Place Basse to Cœur Transport.
• Visible from the promenade, the Monster's Cellar and the Workshop will once again be revealed to the public.

• Illuminated, the Cathedral can also be admired from the promenade. Initially accessible to a limited number of people, it will lend itself to temporary artistic experiences with a view to future developments.
• The Agam pavilion will echo the fountain and green spaces of the slab. This building will serve a technical function. Its upper part may be topped with an information screen or an artistic device illustrating the activities of the residual volumes.

Technical, functional, legal, and financial architectural actions will be carried out step by step, always preserving ample opportunities for evolution.

The Monster has been residing in the depths of La Défense since the 1970s, and its development continued until the death of its creator on June 3, 2005. Invisible to the general public today, it will be showcased as part of the project to enhance the space.