Where on earth do you go to film a show that doesn't look like anywhere on earth?
It's the pickle Game of Thrones producers once found themselves in: they needed a place that could appear as a frozen wasteland, inhabited by "wildling" tribes and the deadly Undead.
The answer? Iceland.
The shockingly beautiful country is fiercely protective of the series that helped transform tourism into one of its most booming industries.
Ever since the show first featured Iceland in season two, glimpses of its breathtaking landscapes have attracted fans from all around the world to the small north Atlantic nation.
In fact, so powerful is the "Game of Thrones effect", it's been credited as a key factor behind the extraordinary swell in annual tourist numbers — from 566,000 in 2011 when it premiered, to more than a whopping 1 million by 2015.
Over the past six years, Thrones creators have filmed key scenes at locations across Iceland.
These have included Lake Mývatn and the ethereal lava fields of Dimmuborgir in the north, the Höfðabrekkuheiði hiking area near Vik, on the island's south coast, the Svínafellsjökull glacier near Skaftafell and Thingvellir National Park near the country's capital of Reykjavik.
A number of those places are remote and difficult to access — in some cases, a fair way off the beaten track — and, pre-Thrones, often overlooked by tourists.
That's where the show's Icelandic location manager, Einar Sveinn Thordarson from Pegasus Pictures, comes in.
He's worked with Thrones producer Chris Newman since the show first moved to Iceland — and revealed to news.com.au there's been one major change in the production over that time.
"One script leaked like two years ago," he said, adding that the writers had become "very protective" since then.
Einar explained: "Before that, [writers] were pretty cavalier about it. I'd just have my script lying in my car.
"But now we get briefs and they've become more protective. It's different, like we'll be filming a fight scene and we won't know the context."
Here are some other secrets from the real-life set of Game of Thrones:
JON SNOW AND YGRITTE'S LOVE CAVE
Sex and nudity features pretty regularly on the show, but Jon Snow losing his virginity to wildling Ygritte in a steamy cave is up there as one of the most iconic scenes.
(Don't forget that it's the moment that gave us: "You know nothing, Jon Snow.")
Einar found the perfect real-life cave for the spicy love scene to take place — a cave called Grjotagja, near Lake Myvatn in northern Iceland. It even featured a romantically ethereal aquamarine hot pool, perfect for the couple's post-sex skinny dip.
During their pre-filming location checks, Einar and the producer had a trial run of the thermal spa and stumbled into some roadblocks.
"We actually went swimming to see if it would work, but it was really, really hot," he explained, adding that they — unsuccessfully — tried to cool it down with ice cubes.
"And the water was very clear ... that was a problem because Rose (Leslie, who played Ygritte) had it written in her contract that she couldn't have that much nudity."
It meant the famous scene was actually shot in different parts: a naturally-formed rock archway around the lake was dressed to look like the cave's entrance, while an exact replica of Grjotagja cave was created in a Belfast production studio.
With the help of the Undead dragon Viserion, the Night King was finally able to smash his way through The Wall in Game of Thrones' explosive season seven finale.
It spells very big trouble for the good people of Westeros.
The Wall is such a mammoth structure, many fans — including myself — could be mistaken for believing it was entirely the work computer-generated imagery.
But in the southernmost point of Iceland, near Vik, it exists, although as Einar admitted: "In post-production they made it, like, 10 times higher."
Easy has clearly never been the objective of the production crew, and the remote and often rugged landscapes they choose in Iceland proves it.
The spectacular coast of Dyrhólaey, used for scenes at Eastwatch, was not easy to get to.
The 100-plus cast and crew had to navigate through a private farm and park their trucks on the edge of the black sand beach, before making the trek over to the cliff face, which would be used as The Wall.
Luckily, none of the cast gets precious about maintaining A-list status on set.
"They don't have their own trailers, they're sitting there at the table with us, there's no nonsense," Einar explained.
THE REAL-LIFE DANGERS BEYOND THE WALL
In a country where the temperature can drop to -30C in winter, working outside is going to be a bit of a nightmare.
To capture the epic snow-covered landscapes of beyond The Wall, the show's cast and crew had to brave extreme temperatures, including gale-force winds.
"Sometimes we're out there when you have a forecast where it's like 'you should stay at home,' and our insurers probably wouldn't have been too happy with us," Einar said.
"But that's how we work. We go out in the storm and we shoot."
He described the moment they were filming in a freezing cold canyon, and were forced to halt production when one actor began to really struggle.
"They [the actors] were nearly exhausted in one of the fight scenes, and we had to stop for one of them. They were all treading in snow, in heavy costumes, over and over ... it's really tough."
During winter, the crew have to head into the frosty wilderness in the darkness using super jeeps and four-wheel bikes — often making the last part of the trek on foot, carrying all the equipment — and prepare everything for filming under work lights.
When the sun finally comes up between 10 and 11am, they've got about four hours to film before they're packing up in the darkness again.
And there's no special treatment for the stars, either.
"They were out there for hours, there was no caravan with a latte on hand. They had a fire in a bowl close by to huddle up for warmth, but they just had to stick it out. They're not just pretty faces — they're tough cookies ... it was not easy," Travelling Viking tour guide Lilja Aðalsteinsdóttir explained to news.com.au.
SECRET ALLIANCE TO PROTECT THE SHOW
In northern Iceland, which provides a recurring landscape on the show, keeping the tourists at bay has become a bigger and bigger task, given that Thrones tours run frequently through the filming locations.
But the crew have figured out a way around the problem.
"They email all the tour operators and let them know where they'll be filming every day so we can avoid the area," Lilja explained.
She added that when the likes of Kit Harington are in town, Icelanders leave them alone: it's not 'their way' to bother celebrities.
Incredible, really, considering some filming locations in the north of the country were established in a town of 400 people — and 200 Thrones cast and crew members had turned up.
So will we see more of Iceland in season eight?
It's likely, Einar told news.com.au
"I'm trying to secure a lot of them [Iceland locations] at the moment," he said.
Game of Thrones Season 7 is released on Blu-ray and DVD on 11 December from HBO Home Entertainment.