Archaeological crypt of Saint Esprit

Hidden beneath the Luxembourg City’s Justice quarter lies a remarkable heritage site: the crypt of Saint Esprit, an underground archaeological space preserving the vestiges of a medieval convent and military occupation. Long buried, it is now entering a new chapter becoming accessible to the public.

A sacred origin

The crypt holds the remains of a Franciscan convent of Poor Clares, founded in 1234 by Countess Ermesinde. This cloistered religious community remained active on the Holy Spirit Plateau until 1690, when the nuns were evicted on the orders of Louis XIV, and the buildings were repurposed for military use. Buried beneath centuries of urban development, the site was rediscovered during archaeological investigations between 2001 and 2003, revealing preserved walls, painted plaster, tile floors, and nearly 300 burials under the choir and cloister walkways.

A military and urban layer

Following the convent’s dissolution, the site was absorbed into the fortress system and later used as barracks for French, Prussian, and German troops. The archaeological layers also include 19th-century military artefacts - buttons, buckles, coins, pipes - testifying to the site’s complex evolution from sacred seclusion to utilitarian defense.

Rediscovery and protection

In 1996, preliminary studies ahead of the construction of the Cité Judiciaire revealed the presence of significant medieval remains. During the court complex’s construction (2003–2008), the vestiges were carefully protected under layers of sand and rubble. In 2023, the Institut national pour le patrimoine architectural (INPA), in collaboration with the Institut national de recherches archéologiques (INRA), began the removal of 3,000 m³ of backfill, once again bringing the structures to light.

A living link to the past

The crypt is a rare archaeological site where one can trace, in situ, the transformation of space from a place of prayer and penance, to one of military strategy, and now, judicial authority. Its story reflects Luxembourg’s own layered identity - religious, fortified, civic - and its careful unveiling is a testament to the country’s commitment to preserving, interpreting, and sharing its heritage with the world.

Guided tours

The Luxembourg City Tourist Office occasionally offers the opportunity to visit the crypt as part of regular guided tours.  When choosing a tour, please make sure that there is a reference to the crypt in the description. The crypt can also be integrated into a city tour with a personal tour guide at any time. If you are interested, please contact us by e-mail at [email protected].