The world of Westeros in Game of Thrones is huge and that, by no means is an exaggeration. The world is so large that people have had to refer to the map countless times just to place one of the characters. It's so huge, that we haven't even seen a majority of it in the HBO series.
Around 125 Minecraft players have taken the world of Westeros and built a majority of it in Minecraft. It's called Westeroscraft.
The project is lead by Jacob Granberry, who has revealed a bit of information about how far they have progressed with the Westerocraft project and how they are getting the job done (the answer is mods, it's always mods):
I would say the world is at around 70% completion…we've developed a custom launcher for the game that comes packed with our WesterosBlocks mod which includes over 50 new custom blocks and textures specifically made for our server. So, we completely repainted our map with new textures, and some of our old builds we are building over bigger, better, and more realistic. That Kings Landing render from a few years ago? Yea, we are remaking that entire city again.
Westeroscraft is big enough that Isaac Hempstead-Wright the actor that plays Bran Stark narrated the trailer for the world:
Granted, it's a Skype narration – cool none the less.
[Kotaku]
