The Vale of Arryn
The Vale of Arryn, often referred to simply as the Vale, is one of the constituent regions of the Seven Kingdoms. Prior to the Targaryen Conquest, it was a sovereign nation known as the Kingdom of Mountain and Vale. It is ruled by House Arryn, from the Eyrie. Protected and surrounded by the Mountains of the Moon, the Vale is isolated from the rest of Westeros and is accessible only during warmer seasons.
Bastards born in the Vale are given the surname Stone.
The Vale is where the Andals first landed and spread out from during their invasion of Westeros six thousand years ago, though as settlement patterns became established, the Reach became the main population centre and cultural heartland of the Andals. Still, combined with its isolated mountainous terrain, noble families from the Vale are said to have among the purest Andal bloodlines within Westeros. A few noble families from other regions can match them for this, but no other region taken as a whole.
There are many small tribes who inhabit the foothills of the Mountains of the Moon. These tribes are commonly known as hill tribes, and they reject the rule of House Arryn. Although they are dangerous to passing travellers, their lack of organization and less advanced weapons means they pose no real threat to the rest of the Seven Kingdoms.
During the War of the Five Kings, under the regency of Lady Lysa Arryn after the death of Jon Arryn, the Vale followed a strict policy of neutrality until the very last stages, and was thus able to keep its army, the formidable knights of the Vale, and resources nearly intact. The young Lord Robin Arryn, under the wing of the manipulative Lord Protector Petyr Baelish, consented to join the fray at last when they came to the aid of their old allies of House Stark in their campaign to take back Winterfell and the North from House Bolton at the Battle of the Bastards. In the aftermath of the battle, the lords of the Vale and the North hailed Jon Snow, a bastard of House Stark, as their King in the North, thus seceding from the sovereignty of the Iron Throne and joining the Kingdom of the North until Jon pledged himself to Daenerys Targaryen during her invasion.