There is a surprising little alleyway just off the Quai de l'Hotel de Ville by the Seine, around the corner from the Hotel de Ville (City Hall) across from pont Louis Philippe, which I first discovered on my last trip to Paris, in May this year. This narrow building, below, pulls you in to the alleyway with its unusual stature.
Just to the left of this building is the St. Gervais church, (there is also a St. Gervais ski resort in the French Alps. I can't find out who St. Gervais was, though!) and the alley that goes up steps next to it, called place St. Gervais. Leave it to the Europeans to take advantage of every open space and set up a café outside on those steps. Brilliant!
The St-Gervais-et-St-Protais Church is among the oldest in Paris. There are records that date back to the 4th century, saying there has been a church on this site that long. But the way it looks now is from the 16th century. (So new.)
The place next to the church used to be called Crossroads of the Elm, for the large elm tree that used to stand there (and still has photos in the church). I guess a lot of money changed hands in that crossroads.
Also, on Good Friday in 1918, during WWI, a German shell fell on the church, killing 100 people.
Heather Stimmler-Hall says, "Today the church is used by the Catholic Community of Jerusalem, whose robed monks and nuns are often seen strolling around the neighborhood. Stop by at 4pm on the first Saturday of the month to hear a free recital on the oldest organ in Paris, built in 1601."
This window faces the place on rue des Barres.