How we made the LEGO® Colosseum set

How a LEGO® set gets designed and made, as told through the LEGO® Colosseum

Regarding how LEGO® sets get designed, we would like to take this opportunity to fully dispel the (relatively) baseless rumors flying around that LEGO® sets are produced following a powerful magical process – involving alchemy, cauldrons and group chanting.

The truth is far more fun, anyway.

To discover more about the *actual* design process, we sat down with Rok Zgalin Kobe, a Senior Designer on LEGO Architecture.

Although each set and theme has slightly different design timelines, given that Rok headed the team behind the largest LEGO set ever – the recent LEGO Colosseum – we thought it would be fun to focus on that particular set. When in Rome, as they say…

Phase 1: The origins

It could be argued that it was Rok’s destiny to one day produce the LEGO Colosseum. As a child, he used to climb the Roman ruins of Emona in his hometown of Ljubljana, Slovenia. Years later, it was in Rome that he and his pregnant girlfriend decided to name their son Rem after the city’s founder, Remus.

So surely Rok was the driving force behind the idea of the LEGO Colosseum? Well…

“That would be extremely self-absorbed,” Rok rebuffs. “It’s the same idea that half the world would have in my position!”

Rok Zgalin Kobe, a senior designer on LEGO Architecture
Rok Zgalin Kobe, a senior designer on LEGO Architecture

Rok reveals how for LEGO Architecture, there is a list of the greatest structures of all time, and this makes the pipeline of future sets more predictable than in themes that rely on popular culture, like the release of a new film.

“The Colosseum has always been at the top of the to-do list. Since 2012, I had already tried it at different scales but it proved hard to do it justice, to convey its monumentality.”

So what changed?

“We were basically given the green light to explore what it would take to do the Colosseum.” Normally, designers would need to establish a price range from a project’s outset. Now, however, Rok could “explore what would be the best execution, without price constraints.”

Phase 2: The concept

The next step was to present at an Internal Selection Event. Internal Selection Events are events held in certain months where a project team submits their latest prototype for review. The first of these funnels is known as the concept phase.

After the first conversations about the new Colosseum took place in February 2019, Rok began creating a concept model, consisting of a “2-dimensional, exterior façade of the Colosseum… one brick thick and just an outline. But the scale of the model has remained completely unchanged since.”

The Colosseum concept model
The Colosseum concept model
These simple, “free-standing curved walls on a board” were enough to “sell the dream”, in Rok’s words, and the model was advanced to the second stage of the selection process: the development phase.

Phase 3: Development

As much as we all love admirin’ our concepts, there is unfortunately some development needed to push things forward.

Unusually, with the Colosseum this development stage was overseen by a new designer. Rok was booked on another concept, so it was handed to Mike Psiaki – who Rok describes as “really great with unusual geometries.”

Mike built the second model in an “amazingly short time for a model of that size”, which was greenlit at a second Internal Selection Event, before returning to Rok for finalization.

Phase 4: Making a brief

Rok only had a month after receiving Mike’s model to “price it up” – something which Rok describes as among the most difficult tasks related to the project. This is known as the brief – where the designer approximates the cost of making the product.

This guestimate is important, because it’s one that designers must stick to later on, knowing that the final model will be vastly different to the current prototypes.

This phase oddly enough also led to an increase in brick count – but that was because Rok looked for ways of making the product more affordable by “substituting a larger, more complex brick for smaller, cheaper ones.”

It was here that Rok began to realize they were close to creating the biggest LEGO set ever. “That was never the goal,” Rok stresses. The main goal was always to “do the best Colosseum that you could do with LEGO bricks. I was always arguing that it needed the façade, the different Doric/Tuscan, Ionic and Corinthian orders. 

The scale demanded that many bricks.”

Phase 5: Finalization

Though the development model looks like the final model, they don’t become buildable until finalization.

Finalization is where user experience is prioritized and all the multiple, unique details that only a master designer like Rok could know are added.

Given its size, Rok worked on four separate partial models corresponding to different sections. The reason for this was to avoid one small change being too time-consuming to implement by containing it to that partial model without extending it to the others.

Yet the models remained so large that Rok was unable to use his desk! He had to work in the atrium of the Innovation House in Billund, where he had to field questions from nearly every project manager, designer and marketeer who walked past!

Phase 6: Heat test

Among the most stressful moments in a LEGO designer’s life is when the product of months, sometimes years, of hard work… is shoved into an industrial oven...

No, we aren’t just horrendously cruel, there’s actually a reason for this. (We promise).

The heat test simulates years of weathering on LEGO elements, and is a step that all prospective LEGO sets must pass to ensure they are durable enough to be sold.

For a model of this size, this outcome was perhaps the most unknown. In trying to counter its weight, Rok and his team created a strong oval base for the Colosseum to provide stability, reduce the ‘fixed’ points to allow for greater flexibility and – in theory – reduce the risk of shattering.

“But only in theory is there no difference between theory and practice!” as Rok put it. “My heart was pounding as model coach Charlotte Niedhardt and I were about to lift the now severely weakened model from the industrial oven…” 

Reader, it worked.

Step 7: Building instructions

Returning from the high of not having their dreams burnt to a crisp, Rok and Charlotte focused on making their model buildable. Here, the ingenuity of Building Instruction expert Martin Højen Holm Buk was deployed to find solutions to even the trickiest of problems.

“We collaborated constantly to ensure we didn’t design something that couldn’t be built using the building instructions”, recalls Rok, “When you make something with LEGO bricks, it has to be built in a logical way, so the experience itself isn’t too confusing.”

Step 8: The End

The final model quality meeting took place in August 2019—barely half a year since the first discussions about the product took place. Given that this was the biggest LEGO set ever built, surely this is longer than other projects Rok had worked on?

“The deadline didn’t differ than much from the regular LEGO design process, although I wasn’t involved in too many other tasks in the meantime. But even though it was four times bigger than my previous biggest LEGO set, I didn’t have four times the time!”

It then took over a year for the set to be released to the public, in November 2020, during which Rok spent the vast majority of his time working on other projects.

“It’s exciting to go back to the launch though,” Rok recalls. “Everyone goes crazy about the Colosseum, and in your mind you are already a year in the future.”

And that, dear reader, is by-and-large how a LEGO set is designed and made. Of course, there are some parts we’ve omitted, but sometimes it’s good to have secrets… now… where did we put our cauldron?

Looking for more?

Check out the Adults Welcome homepage to see our collection of adult-focused sets and articles!