High Heart is a very tall hill sacred to the children of the forest in the riverlands. Around its crown stands a ring of thirty-one weirwood stumps. The hill is considered a safe place due to its relative height compared to the very flat surrounding land, making it nearly impossible to be approached unseen.
According to song, during the Andal invasion the Andal king Erreg slaughtered children of the forest, their animals, and their First Men allies at High Heart, after which his men cut down the weirwood grove. According to True History, however, the children had left the region long before the Andals arrived.
A Storm of Swords
Arya Stark and the Brotherhood without banners rest here one night while travelling south, in order to meet with the ghost of High Heart and to gather information on the whereabouts of Lord Beric Dondarrion. After having found Lord Beric and heading back north, the brotherhood return to High Heart and again meet with the ghost of High Heart, this time she meets Arya but becomes distressed, believing her to be associated with death.
No harm can ever come to those as sleep here.