Game of Thrones: nine things you may not know

17 February 2014 Last updated at 07:47

Think you know everything about Game Of Thrones? Well read on to find out....
Chris Newton
Game of Thrones executive producer, Chris Newton (being interviewed here) had been filming in Iceland for other productions and was the one who recommended the Beyond The Wall scenes be filmed there.
Game of Thrones Iceland filming
The cast and crew only ever had a few hours of daylight, about four or five hours a day, to work with in Iceland. The crew would get to location and set up really early in the dark. As soon as the sun rose, filming could start.
Jon Snow
According to the executive producer Chris Newman, around 60 real Icelandic Vikings were used as extras for the scenes with the Wildings when they were travelling to the Wall. Einherjar, the Vikings of Reykjavík, feature in the show. They try to keep the memory of Vikings alive.
Volcanic ruins
There was no actual cave in the scene where the Wilding Ygritte wins over Jon Snow in season three, but this is the hole the couple crawled through. Ygritte made Jon Snow break his celibacy to the Watch by making love to her. Producers added a black out screen behind this hole, and the actual scene was filmed in a studio.
Icelandic forest
The thicket of trees in this picture, behind these lava pillars, is the same one Sam Tarly runs through in series three to get away from Craster's Keep. It is one of the few locations in Iceland with a large group of trees. Because of a lack of trees on the island, gas fires were used in the Beyond The Wall scenes rather than real log ones.
Dragon glass
Dragon glass, which helped Sam Tarly kill a White Walker in series three, is actually produced when lava, pushed out from a volcano cools quickly with minimum crystal growth. Dragon glass's real name is Obsidian and was used in the past by Vikings as cutting and piercing tools.
Sam Tarly
When Sam Tarly and Gilly are running away from Craster's Keep in series three, a body double was used for actress Hannah Murray, because she was on another job. Let's hope life gets easier for Sam in series four.
Volcanic ruins
Fake snow was used in series one of Game of Thrones. This is real snow. And one of the sites used in series three during Jon Snow's voyage with the Wildings to reach the Wall. In Iceland, traditional tales say these rocks, which are all over the country, are frozen trolls.
Volcanic ruins
Natural steam springs, like this one, were used to give the impression the cast were walking through snow blizzards, during the Beyond The Wall scenes in series three. The springs were also used in the scene where Sam Tarly is nearly killed by a White Walker when he is saved by the rest of the Watch.