From A Wiki of Ice and Fire
The Rills is an area in the North ruled by House Ryswell. It is located southeast of the Stony Shore, north of Blazewater Bay, and west of the barrowlands. Brandon Stark enjoyed riding in the Rills, where he met Barbrey Ryswell.
It is possible the Rills are an extension of the barrowlands; in the story of the seventy-nine sentinels, deserters of the Night's Watch sought refuge in the castle of Lord Ryswell when they reached the barrowlands.
References and Notes