PARIS — Last summer, 20,000 more people visited St. Sulpice Church than the summer before. With its northern tower shrouded in scaffolding, the French Baroque church is one of the least inviting houses of worship in the City of Light, so I recently went there to find out why it became so popular.

Although the church has an artistic prize, Eugene Delacroix's "St. Michael Vanquishing the Devil," no one seemed interested in it. Instead, tourists were gathered by a marble obelisk on the transept's northern aisle, where a sign said: "Contrary to fanciful allegations in a recent best-selling novel, this is not the vestige of an ancient pagan temple."

With 57 million copies of Dan Brown's "The Da Vinci Code" in print, it seemed clear that the people visiting St. Sulpice on the Left Bank were literary pilgrims. They were following in the footsteps of the monk Silas, who goes to the church seeking the key to a secret about Christianity that simply doesn't exist, according to St. Sulpice.

Never mind. Fans are coming in ever-increasing numbers to "Da Vinci Code" settings in France, England and Scotland, inspired by the book's gripping plot, exotic cast of characters and shocking reappraisal of church history.

With this past Friday's release of the highly anticipated movie version of the book, denounced by the Vatican, the stream of "Da Vinci Code" pilgrims to Europe is expected to reach flood levels this summer.

In February 2004, Paris Muse, a walking-tour company, launched the tour "Cracking 'The Da Vinci Code' at the Louvre," followed by another that tracks the book's adventures through Paris. Company founder Ellen McBreen said more than 800 people have toured the Louvre with her guides, seeking messages in the "Mona Lisa" and the "Virgin of the Rocks."

Steve Born, marketing vice president for Colorado-based Globus tours, read "The Da Vinci Code" in the fall of 2004 on a plane headed to Switzerland.

Last summer, the company launched two related tours: "Breaking the Code," a nine-day package to Paris, London and Edinburgh, and a 15-day "The Secret of Da Vinci" trip that adds Rome and Milan, Italy, and Geneva to the itinerary. The two departures of each tour, offered again in August and September, are already sold out.

At the Ritz Hotel, where the book's hero stays while in Paris, a "Ritz and Da Vinci" overnight special runs about $800.

Staff members at Eurostar have found more than 1,000 abandoned copies of "The Da Vinci Code" on trains between Paris, London and Brussels, Belgium, since its publication. That gave the high-speed railway an idea. It is partnering with Columbia Pictures to promote the movie and with government tourist authorities in France, England and Scotland, all of which offer "Da Vinci Code" touring information on Web sites (franceguide.com, vis itbritain.com, visitscotland.com).

SMILE HAS INSPIRED FOR 500 YEARS

Eighty percent of Louvre visitors say their objective is to see the "Mona Lisa," or "La Joconde" ("the smiling one" in French). No one knows why she smiles or for certain who she is, though she is generally thought to be a Florentine noblewoman. Leonardo da Vinci worked on the painting from 1503 to 1506 but never considered it finished. He took it with him to France, where he lived at the end of his life at the behest of Francis I, in whose arms he is said to have died.

Thanks to Francis, the Louvre has five of the 19 major paintings by Leonardo now in museums around the world.

The "Mona Lisa" was stolen by a Louvre workman in 1911 who wanted to return her to Italy; it took museum officials 24 hours to realize she was gone and almost three years to get her back. Artist Pablo Picasso and poet Guillaume Apollinaire were briefly suspected of stealing the painting as a prank to promote modern art.

Raphael, Ingres, Delacroix and Corot were inspired by the "Mona Lisa." Marcel Duchamp painted her with a mustache. Nat King Cole crooned about her. She traveled to the U.S. in 1963 and to Tokyo and Moscow in 1974 but is not expected to leave the Louvre again.

Last year she was encased in a climate-controlled, bullet- and UV-proof display at the center of the redesigned Salle des Etats, a $6.2-million project underwritten by Nippon Television.

— Susan Spano