Public granted first-time access to 13th-century crypt in Luxembourg City

Beneath the justice quarter on the Saint-Esprit plateau lies a long-hidden archaeological treasure: a crypt containing the remarkably preserved remains of a 13th-century convent. After months of careful preparation, this unique site – linked to the origins of the Order of Saint Clare convent founded in 1234 by Countess Ermesinde – is about to be opened to the public for the first time.

The first archaeological discoveries at the site date back to 1996, when preliminary surveys ahead of the justice quarter's construction revealed significant remains of the convent. From 2001 to 2003, more extensive excavations uncovered a series of well-preserved medieval and military structures.

To protect the remains during the building works between 2003 and 2008, the entire area was carefully backfilled with sand and rubble. In 2023, the National Institute for Architectural Heritage (INPA), in collaboration with the National Institute of Archaeological Research (INRA), began the challenging task of removing 3,000 cubic metres of compacted fill. This process made the crypt and its historic features visible again after nearly two decades underground.

Minister for Culture Eric Thill presented the reopening as a milestone in the preservation of national heritage. He emphasised that understanding how people once lived and how society has evolved over time is essential to shaping Luxembourg's identity.

The crypt offers a striking opportunity to see where the Clarissan nuns lived and worshipped centuries ago, and to connect past and present through architecture, according to Thill.

A new tourist attraction

The culture minister also pointed out the site's potential to strengthen cultural tourism. He noted that around 20% of visitors to Luxembourg are drawn by its heritage attractions, and a site like this – located in the very heart of the capital – adds a valuable new stop to the country's cultural offering.

The excavation has not been without difficulty. The INPA's Jean-Jacques List explained that the sand and stone used to preserve the site was never intended to remain in place for so long. It had become heavily compacted due to years of pressure from above, and removing it required a delicate combination of mechanical loosening and suction techniques, an effort that demanded great care to avoid damaging the archaeological remains, according to List.

Due to safety constraints, the crypt is currently only partially accessible via a secure viewing platform. However, long-term plans are already in motion and in late 2024, five scenography firms were invited to propose preliminary concepts for a future museum trail.

One of these proposals will be selected in the near future to guide the creation of a permanent visitor experience. The final design, coordinated by INPA with support from INRA and the architecture firm Teisen & Giesler, is scheduled to begin in 2026 and will take two years to complete.

In the meantime, visitors will have their first chance to explore the site during the LUGA – Luxembourg Urban Garden 2025 exhibition. From 14 June through to the end of October, guided tours will be offered every Saturday morning at 11am by the INPA. Participants will have access to the viewing platform to appreciate the scale of the crypt, understand its historical context, and discover the five proposed scenography concepts.

The inclusion of the crypt in the thematic tours run by the Luxembourg City Tourist Office (LCTO) is also under consideration.

Anyone interested in history, heritage, or simply curious about what lies beneath the city is invited to register for guided tours by emailing info@inpa.etat.lu or calling (+352) 247-86650.