The Church of St Sulpice has many attractions - notably its Delacroix mural. So it is a matter of deep regret to church officials that most visitors are now attracted primarily by a huge bronze candlestick, used by an evil albino monk to batter a nun to death in Dan Brown's best-selling novel, The Da Vinci Code.

Some 20,000 people have visited the Left Bank building over the summer, most in search of the vivid murder scene set in the church.

With more than 10 million copies sold worldwide - 500,000 in French - The Da Vinci Code has now given birth to its own tourist industry: three companies have recently launched tours of Paris taking in the book's principal locations - the Gare St Lazare, the Ritz, the US Embassy and the Louvre.

The Louvre's official position is disdainful. 'None of our curators will talk about the book. It's a work of fiction and we don't see it as our job to discuss it,' a woman in the press office says.

But, at the information booth, Daniel-Richard Leroy is more helpful. Most intriguing to him is the question of whether Pei's glass pyramid really has 666 panes of glass, as the book suggests, in a deliberate Satanic reference. He has counted only 634: 'It's very simple to calculate, and it's quite obvious that there aren't 666 of them.'

The Da Vinci tourists make their way from the pyramid to cast a quick glance at the Mona Lisa, but are primarily interested in the stretch of parquet where the naked body of the Louvre's elderly curator is discovered.

Officials at St Sulpice are annoyed by the onslaught of visitors brandishing the novel and are angered by the book's distortion of history. Staff are so exhausted by demands for information about the Priory of Sion, which Brown links to the church, that they have hung a terse printed notice on a side wall: 'Contrary to the fanciful allegations in a recent best-selling novel, this is not the vestige of a pagan temple.'

For Janet Fisher, 58, a retired French teacher from Kansas, this notice only adds to the delight of the Da Vinci tour. 'I read the novel with my book club last year. I knew there were inaccuracies, but the more I got into the book, the more I wanted to know how much of it really was true,' she says.

Most of the Da Vinci Code tourists are American, and many believe that the book's popularity is partly responsible for the return of US tourists after the Iraq-related boycott.