Basilisk Isles

The 'Basilisk Isles are a large island chain off the northern coast of the continent of Sothoryos, south of Slaver's Bay and Essos. One of the few mapped portions of Sothoryos, they are in the extreme south of the mapped world known to the inhabitants of the Seven Kingdoms of Westeros (Asshai and Yi Ti are rumored to be even further due east, but they are unmapped).

In "You Win Or You Die", Eddard Stark warns Cersei Lannister to flee with her children while she can and as far as she can, because when King Robert Baratheon finds out that they are all bastards borne of incest and none of them are his children, his wrath will follow her to Asshai or the Basilisk Isles.