Check out the classic “trilithon” (3-stone) doorway, made of two upright “orthostats” crowned by a third horizontal lintel. Look closely at the huge flat stones lying on either side of the doorway, and you’ll see that each has a round hole in it. It’s possible that these holes acted as pivot points for big wooden gates that swung across the opening. Or, the cavities may have been “libation holes” where folks poured liquid offerings during rituals.