From A Wiki of Ice and Fire
Sable Hall is a castle along the Wall abandoned by the Night's Watch. It is located between Woodswatch-by-the-Pool to the west and Rimegate to the east.
A Dance with Dragons
Lord Commander Jon Snow considers re-garrisoning Deep Lake or Sable Hall with wildlings under the command of Halleck, although neither castle is ready for human habitation yet. Jon later tells Torghen Flint that Sable Hall is garrisoned, although undermanned.
References and Notes