Notre Dame de L'Assomption, which is commonly called "The Polish Church." It sits right on Rue St-Honoré, though I didn't get a shot of its exterior. (Follow the link for that.) It is domed, and its stone has darkened according to its years. I went in expecting to photograph the interior, but it was all prayer business up in there! Even though my iphone is silent, I felt disrespectful getting it out at all. So sorry, no shots of the interior.
Church of La Madeleine, which sits between Place de la Concorde and Place de la Vendome. This is a church that commands respect, what with its pillars that don't quit, its surrounding square, and its eponymous metro stop.