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On the stone steps of the 500-year-old Santa Maria del Popolo church, our tour group huddled around our guide in a tight circle.

"Come closer," the guide said. We leaned in even more.

"Be really quiet inside," he advised. He was holding a tattered, hardcover copy of Dan Brown's "Angels & Demons," and as he spoke, he slipped it into a messenger bag slung around his shoulder. "The priest here doesn't like us. Oh, and don't flash your Path of Illumination maps."

I felt a tingle of the forbidden as I put the yellowed map in my pocket and quietly stepped through the doors. The church was packed with throngs of tourists and a few dozen people in the pews, waiting for Mass to begin.

A glance to my left startled me: Behind a black iron gate covering a small nook was a shroud-draped skeleton. Its head was cocked to one side and its hands crossed over the chest.

Demon? Angel?

I'm not a Dan Brown fanatic; I casually started the blockbuster book on a recent flight to Rome from my home in Miami. It was fun and a perfect diversion for a boring plane ride. When I finished, I was intrigued. I wanted to see what the sites in the novel looked like. A few Internet clicks yielded something called "The Official Angels & Demons Rome Tour": a four-hour romp through Rome, past sites featured in the book.

For those of you who haven't read it, here's a five-second recap: Harvard symbiologist Robert Langdon (the main character in "The Da Vinci Code," played in the movie by Tom Hanks) teams up with foxy sidekick Vittoria Vetra (played by Israeli actress Ayelet Zurer), and unravels the mystery behind who is mutilating and killing Catholic cardinals. Centuries-old conspiracy theories abound. Oh, and Langdon saves the Vatican from destruction.

As a reader, I wasn't so much taken with the plot or the papal controversy surrounding the book. Much has been written about the Vatican's reaction to both "Angels & Demons" and "The Da Vinci Code." News reports have debunked Brown's account of the Illuminati. For me, it was the setting - Rome - that was exciting. The locations in the novel were like main characters, not just backdrops to a tantalizing treasure hunt through the Eternal City.

The tour, I hoped, would recreate that treasure hunt and maybe provide some real-life history along the way. It didn't disappoint.

We were instructed to meet on the steps of Santa Maria del Popolo at 9:30 a.m. The nearby piazza was already bustling because the Italian state police were marking their 156th anniversary - I knew this because my husband briefly wandered away to drool over the official Police Lamborghini that transports human organs to hospitals at high speed. (Only in Italy.)

About 24 of us were on the tour, mostly middle-aged Americans and a few English-speaking Italians. Our guide greeted us and gave a brief summary of the book; the majority of us had read it, but it was fun to hear it read aloud in the crowded square. He passed out a copy of "The Path of Illumination," a map of Rome photocopied from the novel, and on the back was the printed riddle that had inspired Langdon, our fictional muse:

From Santi's earthly tomb with demon's hole,

'Cross Rome the mystic elements unfold.

The path of light is laid, the sacred test,

Let the angels guide you on your lofty quest.

In the book, Santa Maria del Popolo is the location of the first cardinal's murder.

After we were given the warning to be silent, we all gathered inside near the Chigi Chapel, which was designed by Raphael and filled with works by Gian Lorenzo Bernini, a 17th century sculptor - including the sculpture of a pyramid, a shape that plays a huge role in the novel.

But we couldn't see any of it. The entire chapel was covered in white plastic and scaffolding. Same went for the "demon's hole," a marble, manhole-sized insert in the floor that covers a subterranean crypt. In the book, the Chigi Chapel was covered due to construction - yet unlike Professor Langdon, our tour group couldn't pull the plastic aside to see the marble, pyramid-shaped wall tombs.

I wondered whether the rest of the sites on the tour would be off-limits too. Director Ron Howard claimed that the Vatican interfered with efforts to get permits to shoot certain scenes around Rome, a charge the church said was purely a publicity stunt on Howard's part. Yet Rome's diocese admitted last year it had barred producers from filming inside two churches because the movie didn't conform to Catholic views.

At the front of the church, the priest began Mass. My husband, raised Catholic in Italy, reflexively crossed himself. I snapped a quick photo of the creepy skeleton on the way out.

As it turned out, the skeleton had nothing to do with "Angels & Demons"; it was an exquisite marble sculpture - by Bernini.

From there, a bus whisked us to St. Peter's Square. The guide discussed the fictional "mystic elements" in the book - earth, air, fire, water - then told a story about Roman Emperor Nero and St. Peter's execution.

We spent about 45 minutes outside the Vatican (we didn't go inside; the tour is banned from entering), listening to the guide explain both Bernini's work and read passages from the book.

Then we hustled back to the bus that took us to the rest of the stops: Santa Maria della Vittoria, the Pantheon, Piazza Navona and Castel Sant'Angelo. True to the book, Bernini's statues of angels were everywhere. We even worked in a stop for espresso, which nearly everyone drank despite the heat of the midday Roman sun.

My favorite spot came midway through the tour, at Santa Maria della Vittoria, where Bernini's "The Ecstasy of St. Teresa," sculpture sits. The priest even came out and smiled at us.

The interior of the church looks like it is dipped in gold, with dazzling murals, sculptures and paintings on every available surface. While somewhat off the beaten path (it's a few blocks from the famous Trevi Fountain), it provided the most titillating history: as a young woman, St. Teresa experienced fits of "ecstasy" while dreaming of angels probing her body with spears. The racy statue inside this church depicts one of her dreams - and even offers a laminated sheet of paper with passages from her eyebrow-raising diary.

In the novel "Angels & Demons," this church was the scene of a particularly gruesome murder; our guide declined to read from the book while inside so he wouldn't offend anyone.

Yet there was something even more macabre inside the church than Dan Brown's imagination: the church's namesake, Santa Vittoria herself.

Her centuries-old martyred body is encased in wax in a glass case - but the wax has cracked at the tips of her fingers. Her bones are visible. She's dressed in an ivory gown and her head, circled in a wreath of white flowers, rests on a little pillow. Her eyes are closed, and her mouth is slightly open, as if she's snoring.

"Oh my God, look," I whispered to my husband, while peering at the tiny woman's face. "You can see her real teeth!"

No need for fiction here - reality was thrilling enough.

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If You Go...

ANGELS & DEMONS TOUR: Adults $78 (56 euros); children 4-14, $73 (51 euros), kids under 4 free. Reservations required; tickets from http://www.angelsanddemons.it. Tours Tuesday, Friday, Saturday, Sunday at 9:30 a.m. Runs four to four-and-a-half hours with coffee break. Tour includes bus and walking. Dress appropriately for visiting churches: Cover shoulders and knees.

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