Atlanta (CNN) How do you move something that's longer than a football field, tall as a four-story building, weighs almost six tons and, oh yeah, is a national treasure?

With extreme care -- and a lot of expertise.

Later this week, cranes are expected to pluck a colossal painting depicting a Civil War battle from an Atlanta museum that was its home for nearly a century.

The painting, sliced in two and rolled onto enormous steel spools, will be placed on two flatbed trucks for a 12-mile journey to its new home, the Atlanta History Center in the city's Buckhead neighborhood.

Moving an artwork this big is an ambitious engineering endeavor and requires a small army of specialists, from art conservators to crane operators.

And like the aging painting itself, the story behind the artwork, "The Battle of Atlanta," is almost larger than life.

Why was it painted?

Imagine what life was like in the United States before movies and television -- not to mention CGI and other forms of augmented reality. You had to go to the circus or squeeze into a courtroom gallery at a juicy murder trial to find an attraction with a "wow factor."

In the late 19th century, along came paintings called cycloramas -- massive, 360-degree renderings of landscapes, city skylines and war, including this one about the 1864 Battle of Atlanta. The painting was intended as a tribute to a Northern victory.

A rendering for a typical cyclorama.

Cycloramas were about making big bucks, and companies turned them out as fast as they could. Sometimes they would make two copies.

After a year or so in one spot, the paintings -- the IMAX theaters of their day, according to Jackson McQuigg of the history center -- were rolled and moved to another round building to be displayed before new crowds of customers.

Although the heyday of cycloramas in the United States lasted only a few decades, 72 full-size works still exist across the globe, the International Panorama Council told CNN. Not all are on display. China is the most productive country at creating new ones.

Painters, most from Europe, take a break from the Battle of Atlanta project in Milwaukee in 1886.

'The horrors of war'

Really big show 42

Height of painting in feet 49

Height after restoration in feet 359

Circumference in feet 371

Circumference in feet after missing piece is restored 12,000 Estimated weight of painting in pounds, including fiberglass backing 14

Number of panels 7-8

Amount in feet of sky that will be returned to top of painting 6 X 49

Size in feet of vertical section trimmed to fit into the old building; it will be repainted in the new building.

To paint the Atlanta battle, the American Panorama Company in Milwaukee employed a small army of artists -- OK, maybe 20 guys, most from Europe -- to create a work "intended to please Northern audiences" (read Yankees).

The Battle of Atlanta, fought on the afternoon of July 22, 1864, was a decisive moment in the war, and many historians say the fall of the city more than a month later -- during a time the war was grinding on -- helped re-elect President Abraham Lincoln.

As shown in the painting, Rebel troops have broken the Union army's line and federal reinforcements are riding to the rescue. One vignette shows Federal commander Maj. Gen. William T. Sherman and an ambulance carrying the body of one of his favorite subordinates, Maj. Gen. James B. McPherson.

The focal point of the sprawling painting is fierce fighting around a house, with Confederates firing from behind cotton bales. Federal troops and cavalry are rushing toward that point.

"It is the moment when you are on the cusp of Federal victory," said Gordon Jones, senior military historian at the Atlanta History Center.

Charlie Crawford, president of the Georgia Battlefields Association, said the artists did a good job of capturing a moment: "The scene captures the horrors of war: Dead and dying men and horses, broken equipment, dust, dirt (and) smoke."

How did they paint it?

The artists came to Atlanta twice and studied the landscape from towers. They interviewed veterans of the battle and made sure their paint colors matched Georgia's red clay and pine trees.

Photographs of 1/10-scale sketches (above) were distributed to the artists, who worked on scaffolds under the direction of the lead artist, filling in grids projected onto Belgian linen.

These guys were really good at their craft. One artist might specialize in horses while another focused on human figures and faces. They made two copies of the Battle of Atlanta painting, although the second no longer exists.

"The veterans (who visited) might say, 'I could feel the bullets whizzing by my face.' Sometimes, they would want to say, 'There I am right here.'" -- Gordon Jones, Atlanta History Center

While they got a few things wrong -- "Old Abe," the bald eagle mascot of the 8th Wisconsin Infantry, wasn't really at the battle, and there were no clouds on that muggy day -- veterans and their families were impressed by a work of art that vividly captured the sound and fury of battle.

"This was a way for the veterans to share their combat experience. This is better than going to the battlefield," Jones said. "When you see this, you can say, 'Son this is what I did. This is my experience.'"

Boosting the 3D effect

The painting debuted in Minneapolis in the summer of 1886. After a few moves and a lot of financial distress for owners, the Battle of Atlanta in 1892 ended up in Atlanta -- but not before tweaks were made to appease a Southern audience.

Museum officials decided against building a new revolving stage like this one used at Grant Park location.

A knot of frightened rebel prisoners was repainted as fleeing Union soldiers. And a newspaper ad came up with an alternative fact to promote it: "Only Confederate Victory ever Painted."

Cha-ching!

In the really old days, viewers would simply climb onto a wooden platform to gaze at the painting. A large revolving stage was added 35 years ago.

But while patrons might enjoy the recorded narration and spotlights on certain battle features, they never got the full effect of being able to turn around and see the entire painting.

The diorama is removed at the old location. A new one will be built, but it will still feature 128 plaster soldiers.

Officials in the 1930s came up with another way to promote a 3D effect. They added replica cannon, railroad tracks and 128 plaster soldiers to a diorama built between the painting and the viewing platform.

Why move it?

By 2014, the Atlanta Cyclorama & Civil War Museum was feeling its age and attendance was mostly in decline. Zoo Atlanta, which sits next door to the Cyclorama in the city's Grant Park neighborhood, wanted to expand.

What to do? A decision was made to move the city-owned painting into a new building at the Atlanta History Center. Observers worried the old building was contributing to the painting's slow deterioration. A recent visit to the brick-walled, circular room showed some water seepage on the floor.

"In our eyes, we know it is just an illusion. In the 19th century, they had never seen anything like this, the scale and the color." -- Gordon Jones, Atlanta History Center

About 50 people, among them German and Swiss experts, have worked at the Grant Park building to prepare for the move. Many more are finishing its new home in Buckhead.

Officials traveled to the Gettysburg battlefield in Pennsylvania to glean ideas from a similar project a decade ago . There they spoke with Sue Boardman, a Licensed Battlefield Guide who served as research historian for the Gettysburg Foundation during its project. She understands the stakes when moving such a rare and unwieldy piece of art.

"For all of us ... there is no room for mistakes," she said. "It is a piece of history that is irretrievable."

A vivid scene from the Battle of Atlanta is rolled onto a large scroll.

The tricky part

The technology used to "scroll" a painting for a move is a little bit old and a little bit new.

Workers spent much of 2016 preparing the painting. Strips of cloth were added for attachment points used in the scrolling. Conservators went over every inch, looking for loose paint, said McQuigg, vice president of properties for the Atlanta History Center

A worker installs hardware needed for the scrolling of the painting.

Then came the tricky part. The twin 45-foot-tall metal scrolls were assembled so the painting could be rolled, using a rail system with trolleys. Crews installed various pieces of hardware to help connect the canvas and the giant scrolls. There were many steps in preparation for the scrolling.

"Imagine a flat piece of canvas with paint on it. If you roll it face in, the pressure will be on the edges of that paint. It's going to want to buckle," said Jones. "If you roll it face out, your curve is on the inside. Your outer paint level is going to expand and not buckle."

It took three to four days to slowly roll the linen and backing.

Boardman of Gettysburg said cyclorama workers in the 1880s typically used a pulley system and worked with wooden scrolls that had to be moved as the painting was rolled. It took much longer back then.

One of two wrapped spools containing the painting. A crane will lift both spools through the roof.

Moving day

Officials hope to make it happen this week, but that could slip, depending on the weather.

Two holes will be opened on the concrete roof of the old Atlanta Cyclorama at Grant Park. One crane will do the "big pick" and lift each spool completely out of the building.

A second crane will attach a line to the bottom so that the shrink-wrapped painting can be placed in a horizontal position.

The spools will be loaded onto a flatbed truck and covered with tarps. The two trucks will travel by night, when traffic is lighter, on an undisclosed route to the Atlanta History Center.

Then the spools will be lowered on the second day of the move through a hole in the roof of the Lloyd and Mary Ann Whitaker Cyclorama Building.

Maj. Gen. John "Black Jack" Logan, seen here leading a cavalry charge, saw the painting shortly before he died.

The real work begins

After the painting is rolled out on a new support system, the real work of conservation begins. The old varnish will be replaced and a new lighting system installed. Jones said a 1979-82 conservation project led by Gustav Berger did much to help preserve the paint and the vital supporting lining.

Another piece of Atlanta history will usher visitors into the cyclorama wing. The locomotive Texas , famous for its part in the "Great Locomotive Chase" during the Civil War and its role in keeping freight moving as the city rose from the ashes after the Civil War, also is being restored.

It will return from North Carolina and be added to the museum sometime in May.

Making a huge painting even bigger

The revamped Battle of Atlanta painting also will get even bigger.

In 1921, the installation crew at Grant Park had a wee bit of a problem -- the painting was too big for the building. The solution? Lop off a 6-foot-wide section of the battle scene (fortunately, near an entrance tunnel).

Proper hanging and tension should get rid of folds and wrinkles.

The Battle of Atlanta also lost nearly 8 feet of sky over the years as workers installed it in different buildings.

After nearly a century, all those deleted pieces will be restored.

(Officials will have to decide whether to keep or paint over clouds that were apparently added in 1922 to cover up water damage.)

The restored painting will finally have the proper perspective: Until now, the painting hung like a shower curtain and there were folds and creases. When the painting reopens next year, the aim is to return the "immersion" effect.

The Battle of Atlanta will be displayed in its original hyperbolic, or hourglass shape. Through proper tension at the top and bottom, the painting's horizon will appear closer to the viewer, restoring the original 3D illusion.

You'll be able to see the whole painting: At Grant Park, patrons sat on a carpeted revolving grandstand, which kept them from taking in the entire painting at once. At the AHC, visitors will gaze from a platform 15 feet above ground. The diorama will be rebuilt. The idea is to remove as many obstructions as possible and let the painting make its own statement.

"I think (visitors will) better understand the battle, which is critical to educating people about its importance," said Crawford.

Telling an old story in a new way

Once it reopens in autumn 2018 with related exhibits, visitors to the Atlanta Cyclorama will be able to have a "behind the scenes" view of how the whole production was put together and can spend more time on the platform, looking at every detail of the painting.

A photographer documents a plaster soldier with the face of Clark Gable, star of the screen epic "Gone With the Wind."

The AHC also will tell stories related to the painting, including its correlations to Atlanta's history and the civil rights movement of the 20th century. Officials say the work previously was interpreted in many ways, from extolling the emergence of the "New South" after the Civil War to the "Lost Cause" narrative, which proclaimed the conflict was more about states' rights than slavery. That interpretation is out.

But there's another important reason for preserving the Battle of Atlanta painting, Boardman and Jones say. At Gettysburg, you can still visit the battlefield depicted in that Cyclorama and see for yourself where Pickett's Charge occurred.

Growth and development have erased most of what Atlanta looked like in 1864.

"Since so little of the Atlanta-area battlefield remains, the painting is an important visible reminder that significant events happened here," said Crawford, of the preservation group.

"It makes it all that more important to have this artifact," said Jones.

This is the seventh, and perhaps final, time the painting has been moved.

It's no longer considered a money-making attraction. The painting will still get a lot of TLC as an artifact -- and a very large curiosity.