Moat Cailin

From A Wiki of Ice and Fire

Moat Cailin is an abandoned castle on the northern edge of the great swamp known as the Neck. Constructed of immense blocks of black basalt, only three towers remain out of a fabled twenty: the Gatehouse Tower, the Drunkard's Tower, and the Children's Tower, where the children of the forest once called upon their gods to send the hammer of the waters to smash the Neck.