The framework of the Saint-Louis des Invalides cathedral looks like an overturned boat hull. Built from 1676 onwards by the architect Jules Hardouin-Mansart, the framework is made of chestnut wood that could be found in the 17th century in the Breteuil forest on the site of the current avenue de Breteuil. In the attic floor, a trapdoor communicates with the choir of the church. General Christian Baptiste, director of the Musée de l’Armée from 2011 to 2017, recounts that in the time of Louis XIV a dove was released through the trapdoor at the end of services to show the Holy Spirit to disabled soldiers.