WesterosCraft has created not only one of the most impressive collections in Minecraft, but probably one of the most impressive things in all of the internet. The project takes cues from the "clock-work" intro of HBO's popular series Game of Thrones, which is also an impressive work of its own. No spoilers here, just good old fashioned art.
Building in Minecraft is reminiscent of building with Legos, and there are some pretty impressive landscapes produced in Minecraft. Why do people spend all their time creating work like this? For the same reason you built your own Lego spaceships and houses when you were a kid: the satisfaction of seeing what you created. Though, I'm not sure if they are into the whole "destroy in a maniacal fashion afterwards" thing as well...
King's Landing is the perfect place to start your journey. The Red Keep, the Great Sept, and the Dragon Pit are all featured in this shot. The detail doesn't end at the landmarks. The docks have been filled with individual ships and plenty of unique houses fill the city.
Just outside the Blackwater bay is the home of Stannis Baratheon, Dragonstone. The Minecraft version puts a bit more emphasis on the Dragon part of Dragonstone, but the small island castle represents its namesake well.
To the West is the city of the richest family in the Seven Kingdoms: Lannisport. The Lannisters can see all of their city while sitting on their, presumably, solid gold throne in Casterly Rock.
The Pyke represents its people well. The castle reaches out into the ocean on a chain of islands as if it wished to be more a part of the sea and less a part of the land.
The seat of the old grump with innumerable children, Walder Frey, looks over one of the few places an army can pass from Northern to Southern Westeros with ease, unless the two guarding castles disagree with your passage.
On your way North, you will pass the Dreadfort, home to one of the most disturbed families in Westeros: the Boltons. At least the castle is far more attractive than the family sigil of a flayed man.
Far in the North is the home to the Starks, Winterfell. It's a formidable castle for a part of the world so few want to live in. Perhaps it's what lingers even further North...
The Wall, and more specifically the Castle Black, defends most of Westeros from an ancient enemy. The massive wall of ice and a few undermanned castles are all that remain to hold back the Wildlings from running rampant in the North. At least the Silent Watchers are always at the Wall.
The project has come a long way and still has plenty of work to do. Eventually there are plans to have a fully playable Westeros. It might be hard to believe, but it is likely this project will finish sooner than the next book in the Game of Thrones series, Winds of Winter.