The plot thickened, and so did the crowds of tourists

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 the reason for the dramatic increase in visitors.

Although the church has an artistic prize -- Eugene Delacroix’s “St. Michael Vanquishing the Devil” -- no one seemed interested in seeing it when I visited. 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 bestselling 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 abundantly clear that the people visiting St. Sulpice on the Left Bank were literary pilgrims on the book’s trail. 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 an anticipated blockbuster-movie version of the book, denounced by the Vatican, opening Friday in the U.S., the stream of “Da Vinci Code” pilgrims to Europe is expected to reach flood levels this summer. So, even though literary pilgrims used to mean peanuts to the travel industry, tour operators large and small have begun to take note of “The Da Vinci Code” phenomenon.

Ellen McBreen, founder of Paris Muse, a walking-tour company that specializes in personalized guided visits to museums in the French capital, was one of the first to recognize the trend. “We’d been giving tours in the Louvre but were pretty clueless about the book,” she said. “Then people started asking, ‘Do Leonardo da Vinci paintings have secret codes in them?’ ”

In February 2004, Paris Muse launched the tour “Cracking ‘The Da Vinci Code’ at the Louvre,” followed by another that tracks the book’s adventures through the heart of Paris. 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. He and colleagues started talking about the book and its European settings, most of them well-established attractions already included in Globus itineraries, such as the Louvre, plus London’s Westminster Abbey.

Last summer, the company launched two related tours: “Breaking the Code,” a nine-day package to Paris, London and Edinburgh (starting at $1,699, excluding airfare add-ons for West Coast departure), and a 15-day “The Secret of Da Vinci” trip that adds Rome and Milan, Italy, and Geneva to the itinerary (starting at $2,899, also excluding airfare add-ons for West Coast departure). The two departures of each tour, offered again in August and September, are already sold out, although Globus is trying to get space for additional travelers.

Airline tour companies have jumped on board too. Air France Holidays, for instance, now has a four-night “Mysteries of Da Vinci” package (starting at about $1,619 per person from Los Angeles for round-trip airfare and accommodations but excluding taxes and fees).

At the Ritz Hotel, where the book’s hero stays while in Paris, a “Ritz and Da Vinci” special includes a night in a deluxe double, breakfast for two and an illustrated version of Brown’s novel (for about $800; the “Da Vinci Code” cocktail at the hotel’s Hemingway Bar is extra).

Staff members at Eurostar have found more than 1,000 abandoned copies of “The Da Vinci Code” on trains between Paris, London and Brussels 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 their websites (www.franceguide.com, www.visitbritain.com, www.visitscotland.com).

“The Da Vinci Code” travel phenomenon landed in the lap of Olivia Decker, a San Francisco real estate agent who owns Chateau Villette, about 20 miles northwest of Paris, where the book’s Sir Leigh Teabing hides out. A friend of the author rented the 185-acre estate in 2001 and invited Brown, although Decker didn’t know the chateau was going to figure in the novel until she got a message of thanks from Brown’s wife, Blythe, a year later.

The movie company filmed there last June and July, and now Decker offers “Da Vinci Code” packages of her own, including five nights at the chateau and various guided tours in Paris (starting $4,680 per person).

Tour operators say “Da Vinci Code” trips are most popular among Americans, Brits and Australians, and people book them for a variety of reasons. Some travelers are devoted fans of the novel; others simply appreciate the way the story brings to life places they’ve heard about.

A small percentage of “Da Vinci Code” tourists are proponents of the divine feminine beliefs at the core of the book. For them, visiting places connected to historical and mythological female figures whose stories have purportedly been suppressed is a matter of enlightenment and healing, of spirituality and faith, said Karen Tate, author of “Sacred Places of Goddess: 108 Destinations.”

Lydia Ruyle has been guiding trips to goddess sites in France, Britain, Mexico and Turkey since 1990, most recently for Goddess Conversations, a Colorado-based tour company. “Bless Dan Brown,” she said in an e-mail. “ ‘The Da Vinci Code’ has made the world aware of the Goddess.”

For goddess pilgrims, there are sacred sites to visit all over the world, but the places “Da Vinci Code” travelers want to see are concentrated in Europe.

A handful of them (besides St. Sulpice) have not entirely welcomed the “Da Vinci Code” phenomenon. At Westminster Abbey, where the book is considered theologically unsound, tour guides have been issued information sheets correcting factual errors, and the movie crew wasn’t allowed to film on-site. So director Ron Howard and company shot at Lincoln Cathedral.

The Louvre also allowed the film company to shoot on-site, an unusual event at the great temple of art. Curators have stopped discussing “The Da Vinci Code” in public, and a certain ambivalence prevails about the role the book continues to play in attracting visitors to the museum.

“But they realize that if it gets people in, it’s a good thing,” said Christopher Forbes, chairman of the American Friends of the Louvre.

That’s just what I think when I see people talking about secret codes in front of the “Mona Lisa” or looking for clues at St. Sulpice.