The repurposing of the Saint Pierre des Cuisines church shines a spotlight on a highly complex monument which was built between the 5th and 19th century. As the masonry was in extremely poor condition, some parts had collapsed. This building no longer had a ceiling, and the ground had been dug up several times to uncover older features. After several studies, we proposed a new purpose for the monument, i.e. a 400-seat auditorium with dance halls around the former church. The architectural part was as follows: strict conservation of the parts which offered evidence of the monument’s past; also the new property was “slid” into the monument, both for the stands, ceiling and floor; the latter covers an archaeological crypt which can be accessed from the lobby of the room created under the stands. The auditorium has excellent sound and acoustic qualities, as recognised by leading musicians and critics. The monument’s isolation from the environment required the installation of three horizontal structures on the roof, and for the openings, the installation of external windows and a large soundproofed window opening inwards. This allows the room to be used for daily lessons as well as recordings or concerts.