Whether he’s actually flipping an 18-wheeler end over end down a city street in The Dark Knight or staging intensely choreographed dogfights using period-accurate warplanes in Dunkirk, Christopher Nolan isn’t a filmmaker known for doing things on a small scale.

Nolan’s dedication to this “go big or go home” approach to directing is perhaps most prominently on display in 2010’s sci-fi mindbender Inception, where he takes the viewer on an incredible journey alongside Leonardo DiCaprio’s dream thief Cobb as he and his team traverse the surreal and oftentimes physically impossible mindscapes of their various targets. The depictions of entering another person’s dreams tasked the filmmakers with presenting the unreal as real and the impossible as possible.

While Nolan’s ambitious approach to filming stunts and set pieces makes for some truly spectacular imagery, it can also pose serious difficulties for the cast and crew, requiring unique, inventive and sometimes seemingly unfeasible approaches to capture the required effects on film. Christopher Nolan isn’t the type of filmmaker to let such logistical nightmares to get in the way of his artistic vision.

Here are 15 Secrets Behind The Making Of Inception.

The Paris Café Explosion Was Shot Practically

Inception Cafe scene

While it may sound insane to propose exploding a storefront with two of the film’s lead actors sitting in the middle of the chaos, that’s exactly what Inception’s filmmakers did in the Paris cafe scene.

Leonardo DiCaprio and Ellen Page are sitting around a table in a dream sequence when the dream becomes unstable and the surrounding buildings and objects begin to explode around them. Because Nolan wanted the actors actually in the shot, special effects supervisor Chris Corbould devised a system of air cannons that would safely launch debris around the actors, simulating the building behind them exploding.

CGI was used to polish the images afterward and insert additional destruction, but a majority of what is seen in the explosion sequence was done in-camera with the actors in the line of fire.

They Actually Built The Spinning Hallway And Joseph Gordon-Levitt Did Most Of His Own Stunts

Joseph Gordon Levitt in Inception

In one of the film’s more kinetic action scenes, Joseph Gordon-Levitt finds himself having to fight off two villains while the hallway in which their battle takes place flips, twists and turns in zero gravity.

While these effects could easily be produced strictly using CGI, Nolan’s approach was a much more complicated one.

The crew built the corridor inside a massive centrifuge that could roll in 360 degrees while the actors have their fight scene in the moving structure, allowing them to run up walls and on the ceiling as the set rotated. The cameras had to be firmly mounted to the set to give the feeling of gravity being warped.

Gordon-Levitt said the sequence was the most physically demanding of the entire film and spent two weeks training on the set, familiarizing himself with its movement and perfecting his wire work so that he could film most of the action himself.

The Filmmakers Built An Air Cannon That Could Launch A Van

In one sequence late in the film, Cobb and his team find themselves in the back of a van as it plummets off a bridge into the water below. In order to replicate the effect over several takes, the crew couldn’t simply drop the van over the edge; they needed to have more control over its movement and descent.

The solution was somewhat ingenious in its simplicity: build an enormous air cannon that could launch the van and help to consistently control its speed and force as it plunges.

Actor Dileep Rao, whose character was behind the wheel of the van, said that the sequence took a month to film, with the cast and crew going off to shoot other scenes before returning to tackle the van sequence over and over again before they got everything right.

Nolan Was Working On The Script For A Decade

It should come as no surprise that such a heady and dense storyline would take Nolan a long time to craft. The writer/director said the script had been gestating in his head for a decade before he felt it was ready to be made.

He said he first set up the internal rules of the world and how dream hijacking could be made to work, but that forging an emotional connection between Cobb and the audience was holding up his completing the script.

Nolan said that it wasn’t until he focused the script on Cobb’s journey to reconnect with his wife and estranged children that he realized it was ready to be made, calling those connections the final pieces to the puzzle of Inception’s script.

The Movie Is A Metaphor For Filmmaking

Though the jaw-dropping action and stunt set pieces may be the stars of Nolan’s epic, the movie is impressive for considerably more subtle reasons, too. A true cinephile, Nolan wrote many the roles of Cobb’s team of dream hijackers to be metaphors for the people behind the scenes of a film production.

Ellen Page’s Ariadne constructs the dream worlds and serves as a parallel to a production designer. Tom Hardy’s Eames is the actor who can assume other prople's identities in the dreams. Cillian Murphy as Fischer is the target of the operation and represents an analog of the viewer. Joseph Gordon-Levitt’s point man Arthur serves as a proxy executive producer. And Cobb, overseeing the entire process and pulling the strings, is the director of the operation.

The Casting Process Revolved Around DiCaprio

Inception, Leonardo DiCaprio

Before preproduction on the film even started, Nolan knew that he wanted Leonardo DiCaprio in the lead. Because of this, he took extra care in filling out the supporting roles, making sure they would all compliment Leo as well as possible.

Nolan has said that he admired DiCaprio’s previous work and felt he exhibited the discipline, dedication and relatability that he felt were necessary traits for allowing audiences to connect with the film’s protagonist.

Instead of casting based solely on star power, Nolan chose actors who played off of DiCaprio best and felt right around DiCaprio as Cobb.

The ensemble cast eventually wound up including multiple Academy Award winners and nominees, many of whom – like Michael Caine, Tom Hardy, and Cillian Murphy – have appeared in Nolan’s other projects before and since.

In preparing to film the film’s climactic battle set on a snow covered mountain, the crew was facing a major problem as the filming date approached.

The mountain had no snow.

Cinematographer Wally Pfister recalled a tense few months leading up to filming the pivotal scene, with the crew hoping the Calgary-based set would get the snow needed for the action to take place. Despite their hopes, the art department was sending in pictures of a muddy mountainside instead of the snow blanket they needed.

The team was preparing to make their own snow and use CGI to enhance the visuals instead, but that proved unnecessary. It turned out crew may have gotten more than they bargained for when, the week before shooting was set to start, Calgary was pummeled with the largest blizzard it had seen in a decade, leading to some extremely cold filming days.

Tom Hardy Had To Teach Himself To Ski

Eddie Brock looks inquisitive in Venom

With the mountain finally covered in snow, one of the film’s stars, Tom Hardy, faced another problem all his own in getting ready to shoot. His character was scripted to partake in a thrilling ski and snowmobile chase down the mountain with a group of nameless assassins. The only problem was that Hardy had no idea how to ski.

Hardy was afraid his lack of experience on skis would cost him the role, but in a sort of trial by fire, he taught himself the skills on set.

Nolan strapped Hardy to the back of a snowmobile and sent him down the mountain at 40 miles per hour. In the end, Nolan was impressed by the actor and how quickly he was able to pick up expertise.

Several Real Avalanches Were Created For The Snowy Climax

For his snow chase scene, Nolan drew inspiration from classic Bond films like On Her Majesty’s Secret Service and wanted the scene to culminate in a massive avalanche. To achieve this effect in camera, the filmmakers recruited the help of professional avalanche makers, according to co-producer Jordan Goldberg.

The demolition professionals would fly around the mountain and drop timed explosive at crucial locations throughout the snow banks to create an avalanche once they were detonated.

Several controlled avalanches were set off before the filmmakers got the shots they needed for the final film.

“We tried to do as many things in camera as possible, which is very difficult when you’re in Calgary, where it’s going to be freezing cold and there’s going to be extreme temperatures and extreme weather,” Goldberg said of filming the climactic scene.

The Train Was A Steel Shell Built Around A Semi-Truck

A pivotal moment in Inception involves a freight train barreling through the middle of a downtown street. However, since the road they were filming on had no train tracks and Nolan tries to use as many practical effects as he can, the filmmakers had to improvise to achieve the effect.

Nolan felt it was important to feel like Cobb’s subconscious could bring truly dangerous elements into the dreams and felt that the train needed to have the necessary weight behind it. So the effects crew acquired a semi-truck and extended the frame.

They built a shell out of plywood, Plexiglas, and steel that would fit over a truck and replicate a freight train.

The front of the structure contained approximately 1.5 tons of steel so that it could smash into and push cars out of the way without breaking apart.

The Film Was Shot In Six Countries Across Four Continents

Inception - Saito, Cobb and Arthur

Scenes and set pieces throughout Inception provide a wide variety of settings and locales as the globetrotting protagonists travel the world planning their mission.It wasn’t just the characters traveling - filming of the movie actually took place in six countries on four different continents.

While the majority of the filming took place in and around Los Angeles, other locations included Japan, Morocco, France, England and Canada.

Some of the locations were even familiar spots for Nolan. The massive spinning hallway featured in the zero gravity fight scene was located in a complex of airship hangars in Bedfordshire, England, where Nolan had previously shot scenes for both Batman Begins and The Dark Knight, while interior shots of the Japanese castle in the film’s opening were actually shot on a Warner Bros. soundstage in L.A.

The Score Is A Slowed Down Edith Piaf Song

Marion Cotillard as Edith Piaf in La Vie en Rose

A core concept throughout Inception is how time warps and distorts as the characters navigate the different levels of dreams.

The idea of time manipulation is so integral to the plot of the movie that it even works its way into the the film’s score.

The Edith Piaf song "Non, je ne Regrette Rien" ("No, I do not regret anything") is used as an audio cue that signals a “kick” to another level of dreaming and composer Hans Zimmer used it to help craft the score for the entire film.

Zimmer extracted key notes from the song and manipulated them to construct the score and illustrate how the passage of time changes while dreaming, saying, “all the music in the score is subdivisions and multiplications of the tempo of the Edith Piaf track.”

Cast And Crew Were Locked In A Room Just to Read The Script

It was important to Nolan to keep as much information about his movie a mystery before it was released and he took some drastic precautions to make sure nothing about the project was leaked to the public before he was ready.

Few people had read the full script when DiCaprio signed on as the lead and the rest of the cast and crew had to be locked alone in a room to read it before joining the project.

Special effects supervisor Chris Corbould, who had already worked on Batman Begins and The Dark Knight, said about the secrecy involved, “the script wasn’t allowed out of a room. You go in, and they lock the door and say, ‘Give us a call when you’ve read it.'"

A Hotel Bar Was Built That Could Tilt At 25 Degrees

When Cillian Murphy’s Robert Fischer first realizes he’s in a dream toward the end of the movie, the bar that he’s in begins to shift and tilt at odd angles while he and the other bar patrons remain largely undisturbed.

To create the surreal effect, Nolan needed to make sure that objects wouldn’t be sliding around the set, but that things like the liquid in a glass or a light fixture would tilt and sway realistically as if gravity had shifted.

To that end, an entire bar set was constructed on a platform that could tilt at 25 degrees in either direction from its center point. Cameras were bolted to the set to maintain a consistent point of view as the room shifted

Extras for the scene needed to be auditioned, with about a third of the candidates being unable to remain oriented while the floor below them shifted at various angles.

Nolan Finished The Film Before Deadline And Under Budget

Leonardo DiCaprio in Inception

Despite the incredibly ambitious and technically complicated shoot that went into making Inception, Christopher Nolan still managed to turn the movie in early and at a lower cost than the estimated $160 million budget.

Nolan said at a press conference that, “we were able to hammer through it and we finished early and we finished under budget so we really brought the thing off very, very smoothly which was great… I like having the pressure of time and money and really trying to stick to the parameters we’ve been given.”

Nolan is no stranger to an incredibly efficient shoot. Along with Inception, at least three of his other major offerings – The Prestige, The Dark Knight and The Dark Knight Rises – similarly were finished early and under budget.

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