Jerusalem has been a religious and historical hot spot for millennia, and yet it still manages to surprise the experts.

Why does the city continue to yield unexpected revelations about the days of King David and Jesus — seemingly in plain sight of its residents? One big reason is that it's devilishly difficult to tease out the history of a place where every acre is closely guarded and deeply coveted.

"It's a living city, and it's a city that's been inhabited continuously for thousands of years," Jodi Magness, an archaeologist at the University of North Carolina at Chapel Hill, told NBC News. "Unless, God forbid, the city is ever completely abandoned, we'll never get a complete picture."

Magness is one of the scientific stars of a new movie titled "Jerusalem." The movie, opening this week, takes advantage of IMAX 3-D technology to produce an ultra-big-screen vision of the city, its history and its people.

On one level, the film is an eye-popping travelogue, zooming above centuries-old landmarks and down through the city's claustrophobic alleys, tunnels and bazaars. On another level, it's a study of the human dynamics behind what narrator Benedict Cumberbatch (of "Sherlock" and "Star Trek: Into Darkness" fame) calls "the most fought-over piece of land in history."

That part of the story is presented through the perspective of three young women — a Muslim, a Jew and a Christian. We also get a look at three seasons and places venerated by those three world religions: Ramadan at the Dome of the Rock, High Holy Days at the Western Wall, and Holy Week at the Church of the Holy Sepulchre.



"Here we still have the same Easter like 2,000 years ago," Nadia Tadros, who comes from a Christian family in Jerusalem, says in the movie.

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The sensitivity to all those traditions is one of the biggest challenges facing archaeologists as they try to piece together the story of Jerusalem's past, going back to the Jebusites (also known as the Canaanites) who settled there 5,000 years ago.

Jerusalem's giant puzzle

"Understanding ancient Jerusalem is like trying to put together a giant puzzle, where we're missing most of the pieces and we don't know what the original picture looked like," Magness says in the film. "Everything that we dig up out of the ground is a new piece of the puzzle."



Sometimes there are strokes of incredible luck — as when Bedouin shepherds found the 2,000-year-old Dead Sea Scrolls in a cave in the Judean desert in 1947. But more often, the discoveries come about as a side effect of urban demolition or road construction, or as the result of long negotiations with Jerusalem's current residents.

"Most of the city, archaeologically, is still unexplored and unknown. ... What we have are just little snapshots of what really are random parts of the city," Magness told NBC News.

And even if the archaeologists could dig through the city, Magness said the picture wouldn't be complete. "Every time archaeologists excavate, we destroy the evidence," she explained. "Archaeology is destruction. Once you pull those stones out of the wall, or dig up that floor, you can never put it back."

That's the case with one of Jerusalem's latest finds: a 1st-century Jewish mansion that was unearthed at Mount Zion, just a stone's throw away from where Herod the Great's Second Temple once stood. It's not yet clear who lived in the mansion, but there's a chance that its residents could have included one of the priests who played a role in the biblical tale of Jesus' trial.

James Tabor, a biblical scholar at the University of North Carolina at Charlotte who serves as a co-director for the project, noted that excavators had to dig through layers of rubble from the city's Islamic and Byzantine eras to get to the mansion's ruins. "When we dig down and touch these past civilizations and past stories, it's not as though the people have all disappeared," Tabor told NBC News. "The Armenians, the Catholics, the Greeks, the Protestants, the Muslims and all the varieties of Judaism are all around us."

High-tech windows on the past

Fortunately, there are new ways to identify Jerusalem's ancient monuments without destroying them in the process. Ground-penetrating radar can pinpoint subsurface sites of potential interest before a single rock is broken. Other imaging techniques, such as laser scanning and aerial photography, reveal details that archaeologists on the ground might miss.



A computer graphic from Jerusalem 3D US LP

Still other technologies provide new ways to present Jerusalem's wonders to a global audience. One of the most thrilling scenes in "Jerusalem" starts out with Magness showing a tour group around the monumental walls of the Temple Mount, and ends up morphing into a computer-generated reconstruction of the Second Temple. Other scenes compare present-day settings with how the same location looked in historical photographs or virtual views of the ancient past.

The website for "Jerusalem" provides virtual tours of ancient sites, but there's nothing to compare with seeing the city's past and present come together in 3-D on a giant screen.

"I don't know if Jerusalem ever looked so good," Magness said.

More of Jerusalem's ancient mysteries:

To find out when "Jerusalem" is opening at a theater near you, check out this online list.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.