The Vale is one of the major regions of Westeros and was previously one of the Seven Kingdoms before Aegon’s Conquest. Like many of the other regions, the Vale is largely defined by its geography and climate, which has played a large part in the region’s history. Surrounded by mountains on all sides, the Vale is largely isolated from the other regions of Westeros. As such, historically, it has not been as involved with some of the major wars and conflicts that have plagued Westeros. Due to its mountainous terrain, prior to Aegon’s Conquest, the Vale was referred to as Kingdom of Mountain and Vale. At the start of the GoT series, the Vale is ruled by House Arryn, from the seat of the Eyrie.
Because of its isolation, the land that exists within the mountains of the Vale is pure and pristine. Many inhabitants of the Vale live among this land, while other inhabitants actually live in the mountains that protect the Vale. Traveling through the mountains of the Vale can be very dangerous due to the Mountain Clans that live in the mountains and raid travelers as they pass through. The Vale experiences harsh winters, and passing through the Vale mountains during these winters becomes near impossible. As such, the Vale becomes largely isolated from all other regions until winter comes to an end.
The Vale was the place of landing on Westeros for the Andals during Andal Invasion. Upon their arrival 6,000 years ago, led by Artys Arryn, the Andals defeated the First Men who had previously settled the area. As such, House Arryn is one of the most ancient Andal bloodlines that exists today. After thousands of years of rule, House Arryn wisely bent the knee to Aegon during his Conquest and remained overlords of the Vale and wardens of the East, pledging their fealty to the Iron Throne.
In more recent events, Jon Arryn married Lysa Tully, while Ned Stark married Catelyn Tully, forging a great alliance between House Arryn of the Vale, House Tully of the Riverlands and House Stark of the North. These three great houses, along with House Baratheon of the Stormlands, raised their banners against the Mad King Aerys II in the war that would go on to be known as Robert’s Rebellion. After the war was won and Robert took the Iron Throne, he appointed Jon Arryn as Hand of the King. After discovering the truth that Robert Baratheon had no true heirs and that Jaime Lannister was father to Cercei’s children, Jon Arryn was killed by poison.
Seat of the Vale, the Eyrie, is a great castle that is built atop the Vale’s mountains. It is from the Eyrie that House Arryn presides over the Vale. Though smaller than most of the other great castles, the Eyrie is infamous for its location; atop the mountains, it is nearly impossible to penetrate this castle during a time of war. The Moon Door is one noteworthy feature of the Eyrie; a door in the floor that opens up to the sky, leaving its victims to fall hundreds of feet to their death. The dungeon of the Eyrie, otherwise known as the Sky Cells, are also well known across Westeros – a row of cells carved out of the side of the castle, facing out to the sky. Prisoners in the Sky cells often jump to their death rather than face the terror of being held prisoner in the freezing sky.