You didn't see her on camera.

But Australian Deborah Riley, who spent four seasons on Game of Thrones as a production designer, built some of the most iconic places in Westeros for HBO's television phenomenon.

Ahead of the show's final appearance at the Emmys next week (for which Riley was nominated for her fifth award), she shared some of the secrets embedded in iconic moments from her time on the show.

Everything was bigger for the Clegane-bowl stairs

How do you bring to life one of the most popular fan theories from Game of Thrones, that had no reference point in the books?

Riley had to answer that question when she was tasked with building the staircase where the epic conclusion to the story of the Clegane brothers played out.

Here's the kind of detail you didn't notice, but Riley had to plan for:

"The actor who played The Mountain is obviously a very tall guy and his feet are really quite big," Riley said.

She said her team had to figure out how to fit The Mountain's feet on each step of the staircase.

The-206cm-tall Hafthor Bjornsson plays The Mountain, and while we couldn't find an actual shoe size, here's a snap from his Facebook page:

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Riley also said she had to design the stairs so that Bjornsson and his on-screen brother Rory McCann (who played The Hound) didn't get too exhausted during the gruelling fight scene.

"I think that one took us all by surprise," Riley said.

The Frozen Lake beyond The Wall ... wasn't a lake

One of season seven's most memorable scenes was the last stand of a band of heroes on a frozen lake beyond the Wall (it was also where Daenerys lost Viserion to the Night King).

But the frozen lake wasn't a lake at all.

It was a quarry in Northern Ireland that had been concreted over, then made to look like the icy surrounds beyond The Wall.

Not a lake. Actually a quarry. ( HBO )

"I remember the producer Chris Newman standing there [in the quarry] and saying 'well this could be it. Jon could enter this way, the Night King would stand over there' and all of us going 'OK. Right'," Riley said.

And if you watched that scene, struggling to tell what was CGI and what was real, there's a good reason for that. Most of it was real.

"When you were in that quarry it looked pretty much like as you see it on screen. That's something I'm really proud of because people just don't appreciate, unless you were there, how much was built. How much fake snow went down," Riley said.

"You would never believe it unless you saw. And that's the great thing, because we don't want people to see it. That's the magic of the whole thing."

An American architect in Meereen

The audience chamber in Meereen, designed by Deborah Riley. ( HBO )

This one holds special significance for Riley, who studied architecture at the University of Queensland before making the transition to working in film and TV.

"I had arrived out of nowhere and inherited an art department. You can imagine how nervous I was and how many eyes were looking at me," she said.

She leaned on her architectural knowledge for this set, incorporating references to American architect Frank Lloyd Wright into Daenerys' audience chamber in Meereen.

"I don't think anybody had ever thought before, particularly on Game of Thrones, to bring 1930s Frank Lloyd Wright references to Westeros," she said.

"Recently the Frank Lloyd Wright magazine contacted me and I thought 'Oh no! Here we go. They're going to tell me off'.

"But they loved it!"

Frank Lloyd Wright's famed, 6,000-square-foot Los Angeles mansion was the inspiration for the Meereen audience chamber. ( Reuters: Mario Anzuoni )

The Hall of Faces had real-life inspiration

One of the key parts of Arya's storyline was her journey to the House of Black and White in Braavos, where she learned to become a Faceless Man.

And the Wall of Faces scene, which featured heavily in the marketing for the series, was Riley's handiwork.

Arya and Jaqen H'ghar take a wander through the Hall of Faces. ( HBO )

Understandably, she said trying to design an underground repository of stolen faces was a "weird scenario".

To create the look, Riley recalled a trip she once took to the Ten Thousand Buddhas Monastery and the stone-cut monasteries of India.

The monastery, found in Hong Kong, is actually home to almost 13,000 statues that line the walls of the main temple — not unlike the faces that line the walls of the basement in the House of Black and White in Braavos.

"When you put those two together, you get the Hall of Faces," Riley said.