Location from A Song of Ice and Fire by George R.R. Martin
A slender white castle perched impossibly high in the Mountains of the Moon, reachable only by a treacherous mule path and guarded by the infamous Moon Door.
The Eyrie trades size for impregnability. No army has ever reached its gates — the approach is a single switchback trail up the Giant's Lance, guarded by three waycastles that can hold off a thousand men each. The air is thin and cold, the silence broken only by wind and the occasional scream from the Moon Door — a narrow weirwood door in the floor of the high hall that opens onto empty sky. Lysa Arryn used it as her preferred method of execution, and the blue sky visible through it has a way of making every conversation in the hall feel like a negotiation conducted at knifepoint. The castle must be abandoned each winter when the snows make the path impassable.
Seven slim white towers cling to the shoulder of the Giant's Lance, so high that clouds drift below the walls. The castle is small compared to other great seats — delicate, almost, built for beauty rather than brute defense because the mountain itself is the defense. A narrow sky cell opens onto a six-hundred-foot drop with a floor that slopes gently outward.
Also known as: the Eyrie, Arryn seat, castle in the sky