House Arryn of the Eyrie is one of the Great Houses of Westeros, and is the principal noble house in the Vale of Arryn. Their main seat is the Eyrie, which is considered impregnable.[2][3] House Arryn has at least one other holding, their winter castle at the Gates of the Moon, which was once their main seat.[4] Both of these fortifications sit astride the Giant's Lance, the tallest mountain in the Vale, the Gates of the Moon at its foot, the Eyrie at its top.[3][5]