Sainte-Clotilde Basilica
Looking at the Sainte-Clotilde Basilica, you would think it looks Gothic and therefore built in the middle ages. It is actually "Neo-Gothic" and built much later in the mid 1800's.
While the basilica may not be as known as the landmark cathedrals and churches of Paris, it is notorious in the world of organ players and composers. Many renown organists performed in Sainte-Clotilde, and to this day, they maintain the tradition with organ concerts every week-end.
I always loved the dramatic sound of this instrument and attended several organ concerts there. Concert season will resume in September this year, if you visit Paris and love the organ, this is a great place to be!