Hi. It's a medieval underground with active defense. It was used to protect against possible attackers during this period.

The guide explained at the beginning, just before they went down that originally it was an underground quarry to provide stone for building the church, which is why it doesn't run under it. These tunnels may have provided stone for a chapel that predated the existing church. The quarry has been listed as an important historical monument, but so far the church itself hasn't been listed as such. The church was seriously damaged during various moments of its history and the underground tunnels were sealed off, which created problems of condensation. He did of course give far more details about the history and the uses to which it was put, but it would be too long to explain it all here.

Ces tunnels du Moyen âge servaient à se défendre et à se cacher en cas d'attaque notamment lors des guerres de religion catholiques vs protestants car il y a eu des massacres (St Barthélémy, dans la nuit du 24 août 1572, 30 000 protestants sont massacrés par des catholiques dans les rues de Paris.) Les passages sont étroits afin d'être défendus par très peu d'hommes. Ces tunnels et parfois des villes entières souterraines sont fréquentes dans certaines régions y compris au Moyen-Orient et en Turquie.