Erelas

Erelas was one of the warning beacons of the White Mountains, which stood on the northern border of Gondor. It overlooked the lowlands of Anórien and was the fourth beacon from east to west. The beacon was small and thus not always lit, save at times of great urgency.
Prior to the Siege of Gondor in the late Third Age, Erelas was the fourth beacon to be lit to signal Rohan for aid.