The phrase “it’s big in Europe” might draw some epic eye rolls from those in the States, but in the case of Mortal Engines, it’s true.

Author Philip Reeve released the first of a quartet of young-adult sci-fi novels in 2001 and sparked a massive hit — so massive, that The Lord of the Rings director Peter Jackson wanted to make it his next film adaptation in 2008. As he explained to reporters on the Mortal Engines set in New Zealand last year, that plan fell apart at the time when development on The Hobbit picked up. With the film rights set to expire years later, Jackson felt it best to hand the directing reigns to Christian Rivers, his storyboard artist of the past 25 years.

Now Mortal Engines is finally revving towards theaters at the end of the year. But, let’s face it, Reeves is no Rowling. The U.K.-based book series didn’t have the same impact on the U.S. as Harry Potter, so that first teaser trailer playing ahead of Star Wars: The Last Jedi screenings may have raised more questions than answers for those not in the know.

Mortal Engines is based around the fictional concept of Municipal Darwinism, a system where cities are rebuilt as mobile Traction Cities and roam around the planet devouring smaller cities. (Think Howl’s Moving Castle but on wheels.) It’s in this alternate future where we meet Hester Shaw (Hera Hilmar), a woman on a mission that will lead her to cross paths with a young apprentice, Tom Natsworthy (Robert Sheehan), both of whom are destined to change the course of their future.

With a cast that includes Hugo Weaving, Stephen Lang, Colin Salmon, Jihae, Ronan Raftery, Leila George, and Patrick Malahide, Mortal Engines may end up sparking the next Hollywood franchise — assuming enough people come out to see it.

Last year, Collider joined a group of reporters on the film’s New Zealand set and, over the course of two days, learned the ins and outs of this imagined reality — a reality Jackson says “feels more possible now than in 2008” when he first started working on it. Here’s what we learned:

It’s been approximately 1,700 years since the Sixty Minute War, a great war that lasted 60 minutes but reshaped the world into this post-dystopian society we see on screen.

This world is largely based on the principle of Municipal Darwinism, the idea that mobile cities eat each other with the bigger, stronger cities always coming out on top. Then there are the anti-tractionists, who fight against this ecosystem. According to Jihae, Londoners might call anti-tractionists terrorist, but “they’re actually the protectors of making sure that humankind does not go complete or extinct.”

The producers don’t consider this story to be a post-apocalyptic dystopia. It’s more what happens thousands of years after a dystopia. “The world is coming back,” co-screenwriter Philippa Boyens, another frequent Jackson collaborator, says, “if these f—ing traction engines would stop rampaging all over.”

The great London Traction City was built with the ruins of the London we know, so there will be various recognizable bronze statues and Victorian elements. The transportation system, for one, is based on the look of the London bus system and the London Eye. There are three main sections to London: the Gut, which is where the lower-class blue-collar workers strip newly ingested cities for parts; the Second Tier, where low-to-middle class people, including the historians, dwell; and the First Tier, which is for the more aristocratic one-percenters.

Other locations include Shang Guo, “where they’re becoming more enlightened,” extras casting coordinator Victoria Beynon says. Production designer Dan Hennah explains further that this is the location for the anti-tractionists tucked away in the east. “We’re not saying it’s China. We’re not saying it’s Vietnam. We’re not saying where it is,” he says. Instead, Shan Guo is a mixture of these places. Their “alternate lifestyle,” as he calls it, consists of growing their own vegetables, weaving their own fabrics, and preserving plants and trees — a culture that doesn’t exist in the traction cities. “It’s summer in Shan Guo,” Hennah mentions. “Shan Guo’s a little micro climate.”

Then there’s Airhaven, an area where the city is built up in the clouds. The pilots of airships tend to dress for warmth, since the climate is much colder.