Saint-Sulpice church is located in the Saint Germain neighborhood of Paris in the 6th district metro stop Saint-Sulpice.
The Da Vinci Code states that the Paris Meridian or the Rose Line as the book calls it, runs through Saint-Sulpice church. This is fiction. Yes, Saint-Sulpice has a meridian line but the one in Saint-Sulpice has nothing to do with the once zero-longitude line Paris Meridian. The meridian line in Saint-Sulpice is used to determine the winter solstice and Easter.