The Eglise Saint-Germain-des Pres gave its name to the whole quarter around it (which is also part of Latin Quarter). The church was the intellectual center of Catholic church until French Revolution when the church lost most of its power but the intellectual traditions in this area lived on. We walked into this church to look for Rene Descartes resting place. He had many addresses while he was alive, and his remains also travelled - first he was buried in Sweden, where he died, then later transferred to Paris - to the Eglise Saint Etienne-du-Mont, later to Eglise-Saint-Germain-des-Pres (some sources say that only his heart is buried there). In 1792 it was decided that Descartes should be interred in the Pantheon but nothing has changed so far - his "final address" is still the Eglise -Saint-Germain-des-Pres, between two scholarly monks.
Next to the church is a little garden with a sculpture for the poet Guilliaume Apollinaire, who is credited of coining the term surrealism. He thought that " Geometry is to the plastic arts what grammar is to the art of the writer.".
If one would try to put up signs for famous intellectuals who left their footprints in the area of Saint-Germain-des-Pres, then very little space for pedestrians would be left there. On the busy corner across from Eglise Saint-Germain-des Pres I attempted to snap a photo of Les Deux Magots - a cafe that opened in 1875 in the space previously occupied by the fabric shop and which bills itself The Rendezvous of Intellectual Elite. The narrow slice in front of it is called the Place Jean-Paul-Sartre-Simone de Beauvoir. There are several other famous cafes in the area known as traditional meeting places for intellectuals, for example Cafe de Flore, or Brasserie Lipp,
but we, mathematicians, headed for La Procope following its official address 13 rue de-l' Ancienne-Comedie. (Next time I would like to try the other entrance we missed - at 128 Blvd. St. Germain there is an entrance into the lovely passage built by the ancient Paris wall.)
In this "world's oldest cafe" Voltaire and Napoleon Bonaparte have been patrons and that of course overshadows other guests. French encyclopedists were meeting here, among them Diderot and d'Alambert.
We thought that two hours for lunch will be enough time. Apparently not in this place. We were led to the table on the ground floor. While waiting for food to arrive we had plenty of time to soak in the place where discussions among various celebrities (did I mention Benjamin Franklin, Thomas Jefferson, Robespierre, Alexander von Humboldt, Alfred de Musset, and George Sand?) have taken place in the past.
During our lunch I watched a group of visiting German students who clearly were on budget in Paris but had decided to celebrate there stay in a place where authors from their textbooks once had come. Across from us there was an impatient elderly lady waiting for her date. I was curious to guess who would come. My guess that she is a professor was correct (do we all have some professional marks on our foreheads?). Her date was slightly late, and it was her graduate student whom she had invited for a treat, and his lunch was wrapped in a long lecture on philosophical topics.
I used an excuse "to wash my hands" to find that Dames are one floor up, so I had a chance to peak into other dining rooms as well. One of them even has Voltaire's desk.
The name for the street cafe La Procope is on comes from the fact that across from it was the original house of La Comédie-Française.
We had to finish our philosophically long lunch and rush to the Institute of Henri Poincare to see mathematical models there, but I will write about it more properly later.
We came back to the Left Bank some other day to look for more places of historical-mathematical interest.
Thanks to David Burke to point out that:
"Saint Germain-des-Pres was not part of the Latin Quarter. They were separate, even rival, entities sharing the medieval Left Bank. Philippe Auguste's 13th century wall ran between them. It ran from the Seine along today's Rue Mazarine, up Rue Monsieur le Prince, looped around (actually just inside) today's Place de la Contrescarpe, and down Rue du Cardinal-Lemoine to the river. That wall was built to protect the Latin Quarter."
In several tour guides Saint-Germain-des-Pres and Latin Quarter are mixed together perhaps because today there is no such strict line between them.
Rue de Mazarine leads to Institute de France - the most prestigious institution established by Cardinal Richelieu in 1635 as the official guardian of the French language. Under its auspices in 1666 l'Academie des Sciences was founded - to encourage and protect French scientific research. The domed landmark at the end of this street is the Bibliotheque Mazarine - beautiful museum of the books and the working library.
In 17th century Rue Mazarine would be a place where theater companies set up shops at former tennis courts. A plaque on a present day building at No.12 marks the place where Theatre Illustre that lasted only a year but the name of one of its actors, young Jean-Baptiste Poquelin, forever is written in the history of theater. We know him as Moliere.
Rue de Seine was at one time an address of Legendre. 
Marquis de Condorcet was wearing many hats. One of them was a mathematician, but he was sentenced to death for his political activities.
At the time Victor Hugo wrote his Notre-Dame de Paris (The Hunchback of Notre-Dame) the cathedral was neglected, and even thought to be demolished. Hugo's book was the first work of fiction that brought a city alive, and, as he hoped, the success of the book sparked the public interest and started a campaign to save Gothic architecture. The Eglise Saint-Sulpice is the second largest in the city, only slightly smaller than Notre Dame. The building is very harmonic one, if to ignore two mismatched towers.
The Place Saint-Sulpice infront of the church has the busy Fontaine des Quatres Points Cardinaux in its center. Working fountain in January... For somebody from Ithaca it was hard to believe it is possible in wintertime. This place was beloved place for writers Henri Miller and Anatol France. I believe that some mathematicians have been walking there too, unfortunately they do not usually leave notes about that. Near there used to be the Cafe de la Mairie, favorite of the Surrealists, and of Hemingway, Fitzgerald, and Faulkner, when they lived nearby.
The book must have annoyed a lot of clergy in the church because next to the famous gnomon there is a big sign that Brown's book is pure fiction. There is also a translation of original gnomon's description.
These gnomons in early days were built in several churches but lost their usefulness after powerful telescopes were invented.
Several mathematicians lived near Luxembourg Gardens. At no.12 Rue de Tournon, near the entrance to the Palais du Luxembourg Cauchy and Leverrier lived. Cauchy was a prolific writer - he wrote about 800 research papers. in the late 1750's on Rue de Tournon at No.27 lived Giacomo Casanova, whose name also associates with large numbers but not the research papers...
About our visit at the Institute Henri Poincare next time.
PS. My literary knowledge comes from David Burke's very enlightening book Writer's in Paris.
PSS. March 25 NewYork Times also has a piece about Paris A Paris Farewell by Amy Thomas - sorry if starting March 28 it will not be available...
