The reconstruction project of the spire of the Saint-Denis Basilica is a major heritage and architectural event that will extend until 2030, making it one of the largest heritage sites in Europe. Led by the association Suivez la Flèche, this exceptional project is accompanied by the Fabrique de la flèche (Spire Factory), an immersive construction site and multi-experiential cultural venue. This unique showcase space is designed to allow the public to follow, understand, and experience this historic reconstruction in real time. The Fabrique de la flèche was inaugurated on October 16, 2025, by Mathieu Hanotin, president of Suivez la flèche, mayor of Saint-Denis, and president of Plaine Commune, Marie Lavandier, president of the Centre des monuments nationaux, and Stéphane Troussel, president of the Seine-Saint-Denis Departmental Council, among others.

Specializing in immersive experiences and heritage enhancement, Art Graphique & Patrimoine (AGP), a MEMORIST company, was commissioned by Suivez la Flèche to coordinate the digital component of the enhancement project and develop innovative immersive experiences.

AGP brought together and guided a consortium of 5 companies (Apsulis, Fosphor, Horus, Mosquito, Spectre Lab) to develop a variety of contemporary technological solutions — such as virtual reality experiences — with the goal of transforming the site visit experience into a modern, immersive cultural adventure accessible to all.

A virtual reconstruction of the spire using stone-by-stone 3D modeling.

The first step of the immersive component, prior to the start of the physical reconstruction, was the complete 3D reconstruction of the spire carried out by AGP. 15,228 stones, from structural elements to finely sculpted gargoyles, were recreated identically in virtual form through 3D modeling by specialized draftspeople and stonecutters. This first phase, carried out in collaboration with the chief architects of historical monuments for the Saint-Denis Basilica (Cabinet 2BDM), based on existing historical documentation of the spire (plans, drawings, ancient surveys), validated the project's feasibility and optimized the reconstruction work.

This 3D modeling also served as an essential tool for public mediation. Integrated into various devices (3D films, touch tables, interactive screens, immersive projections, virtual reality), it enriches the visitor experience at La Fabrique de la flèche.

La Fabrique de la flèche: an immersive discovery space.

For the first time, a heritage restoration project of such scale is organized around a construction site open to the public and visitable. The enhancement area hosts a scenographed tour as well as real-life experiences (Craftsmen's Village, stone cutting / forge) and immersive ones, allowing visitors to understand the history of the spire and the feat that its reconstruction represents.

The digital mediation space includes:

• The permanent exhibition: an immersive tour scenographed by the company Vaste, featuring educational films produced by Art Graphique & Patrimoine and Mosquito that trace the history of the basilica and the evolution of its spire.

• The immersive cinema: a 360° dreamlike immersive film, created by Spectre Lab using AGP's digital content, immersing visitors in the history and significance of the spire.

• Another innovative feature: thanks to cameras installed on the scaffolding and managed by Horus Connect, the progress of the construction site will be visible in real time on screens throughout the Fabrique de la Flèche spaces.

A virtual reality experience fully developed by AGP.

One of the major features of the Fabrique de la Flèche is the virtual reality room accessible to visitors by reservation. Entirely designed and developed by AGP, this experience allows visitors to step into the shoes of an architect, master builder, or stonecutter, taking on the challenges of virtual spire construction.

This educational and interactive immersion represents a first in mediation around a heritage restoration site in France.

With this major project, through collaboration with AGP and its partners, Suivez la Flèche transforms this historic construction site into unprecedented multi-sensory experiences, combining heritage and cutting-edge technology.