The county had its seat in Rhedae, a Roman and later Visigoth town conquered by the Franks in 756, together with Septimania.
Louis Fédié (1815–1899), the 19th-century author, amateur historian and president of the Société des Arts et Sciences in Carcassonne, popularised the claim that Rhedae was the village of Rennes-le-Château in his 1880 book Le Comté de Razès et le diocèse d'Alet.
[2] His 19th-century identification is widely disputed by professional French archaeologists and historians,[3] and the precise location of Rhedae remains unknown.
It was probably near modern Quillan, which is a major crossroads town about 20 kilometers south of Limoux in the heart of the ancient County of Razès, now in Aude .
Putnam and Wood have noted the difficulty in understanding how the name Rhedae could have been changed to Rennes-le-Château;[4] and Rhedae was cited as being "located at the crossing point of four major roads: how could this possibly be the case at Rennes-le-Château on its isolated hilltop?