From A Wiki of Ice and Fire
and the location of Sandstone
Sandstone is the seat of House Qorgyle. It lies west of the Hellholt and the Brimstone in the western desert of Dorne.
The Andals who founded House Qorgyle built Sandstone when they fortified the only well around for fifty leagues in the deep dunes of Dorne.
It was rumored that Lord Qorgyle arranged the murder by scorpion of Lord Lyonel Tyrell at Sandstone.
Prince Oberyn Martell was fostered at Sandstone.
References and Notes