The Al Fath Mosque on Rue des Poissonniers in Paris receives thousands for Friday prayer, way beyond its capacity. The surrounding streets are entirely given over to worshippers.

Around the corner is the vast church of St Bernard de la Chapelle, whose doors appear to be permanently padlocked. Amongst local proposals is that of converting the church into a mosque. I'd hazard a guess that this is not what was - during the French Revolution - envisaged by "dechristianisation".

(The photo of the prayers is mine. The church is from Google Street View.)