Check out our exclusive behind-the-scenes production video, below.

At a recent “Roma” crafts panel, “Incredibles 2” director Brad Bird couldn’t disguise his envy of the freedom afforded director Alfonso Cuarón. “It’s a black-and-white film with non-actors in Mexico City in the ’70s,” Bird said. “But when you see the film, it has an epic feeling that’s unlike anything. It’s like being in the spot. It’s an experiential film, it’s like you are there.”

Much of that stemmed fromCuarón’s exacting production process: He took 108 days to shoot, in chronological order. He did did not share the script, parceling out information on a must-know basis, all of which was a challenge for his crew as well as his actors.

Before Cuarón finally gave him a script, Oscar-winner Eugenio Caballero (“Pan’s Labyrinth”) had already created the sets. This forced the collaborators to discuss the creation of Cuarón’s memories of 1971 Mexico in a way that was less about telling a story than recreating a period.

“We focused on things differently than normal,” said Caballero, whose grandparents lived in the same Roma neighborhood of Mexico City. “Instead of talking about story and character, the arc of the characters and their actions, here we spoke more about his own life and his own memories, which triggered my own memories as well. We started building the sets through the details.”

“It was also like an archeological search,” said Cuarón, who dug up memories with Caballero as “more detail and specificity would come out.”

Extensive period research was useful for Caballero, who was tasked with recreating the ’30s-built Cuarón family home. As the original no longer resembles the one where Cuarón lived, they used an exterior facade from the other side of the street. And they visited the original house to measure all the rooms in order to recreate the layout. “We changed everything,” said Caballero.

“The original house had nothing to do with this house,” said Cuarón.

“It’s the heart of the film,” said Caballero. For the interior, they did not want to use a soundstage. Instead, they took a house slated for demolition and rebuilt it. “We wanted real tile and brick and plaster. This gave us the opportunity to create the house Alfonso remembered. We didn’t have that many pictures. The ’70s was an iconic strong design era, but the period, we noticed, was ’60s, ’50s, ’40s, all decades — cars, design, architecture. All these things were mixed and blended. We wanted to contrast the social classes and worlds that collide in this city.”

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“A lot of films fake period,” added Cuarón. “When you do something ’70s, you do things that look so cool, so vintage. No — we wanted to do a film that takes place in the 1970s where this is still not old, it’s the way it was. There’s ’70s cool things combined with ’50s and ’40s and some banality that has timeless ugliness.”

With the aid of the director’s memories, the set decorators tracked down 80 percent of the home’s original furniture, spread out among his relatives. The rest they found or built themselves. They stuffed all the drawers with objects, even if they weren’t going to be used.

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For the second floor, the art department erected sliding walls and a pulley system that went up and down like a guillotine and windows that could expand for more light. The crew shot there for six months.

Caballero found some areas in Mexico City that hadn’t changed much, while others were so dramatically transformed that they could not be used. That meant Cabellero had to construct an entire cosmopolitan city street, Avenida Insurgentes, for the scene when nanny Cleo (Yalitza Aparicio) chases after her charges on their way to a movie theater. “There were so many things we wanted to tell in that shot,” said Caballero, “that we decided to build it from scratch.”

“We knew we wanted to talk about social congress in Mexico,” said Cuarón. “Wherever you set foot, you see details that codify hierarchy and status.”

It was important to give the camera dense details. The filmmaker told Caballero that when he was designing Avenida Insurgentes, “all you know is that I may go inside each shop. They were so rich and detailed.”

Finding an open space to build in was so difficult (even a parking lot next to an abandoned sports stadium wasn’t big enough) that the location manager resorted to Google Maps.

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Few people watching that scene of Cleo passing several city blocks with shops full of people and crossing the busy avenue crammed with cars and pedestrians would ever suspect that it wasn’t “real.” VFX also supplied missing depth and detail.

“There was no sidewalk, nothing, not even asphalt,” said Cuarón. “They had to asphalt the whole thing… it was an archeological situation, finding the buildings, how they were in the period, the fluorescent lights, going around the city with still photographers and rendering. The art department was linked into the VFX in such a detailed way.”

Photo by Carlos Somonte

Special effects master Nico Celis had to organize a burning forest on a freezing night, complete with a falling tree that would sustain through Cuarón’s legendary long takes. It took three connected gasoline tank trucks to feed the fires, and flame retardant to keep the woods from catching the blaze.

Even the watery long opening shot, delivered via complex visual effects, includes the tile, the sky, and a digital plane. True to the period, of course.

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