HOLLOW HILLS. MAGIC CASTLES. AND GREENSEERS INTRODUCTION Hi everyone.  The premise of this essay will be to show that many of the ancient castles of Westeros were strategically built atop hollow hills to harness the magic of the caverns below.  Just as the two greenseers, Bloodraven and Bran do.  There are only two hollow hills named as such in Westeros, and both are openly associated with magic and greenseers, High Heart and Bloodraven’s cave.  HIGH HEART High Heart h