Seat of House Estermont on the isle of Estermont, off the storm-wracked coast of Cape Wrath in the Sea of Dorne. The castle is built of the grey-green stone that gives it its name, and the sea beats at its foundations with every tide.
The Turtle's Isle
The Estermonts bear a dark green sea turtle upon their banner, a fit device for lords whose lands are girdled by salt water. Their isle is rocky and their living modest by the measure of the great houses, yet the blood of Greenstone has mingled with that of the lords of Storm's End, and its sons have stood high in their councils.