This room in the castle is probably one of the coolest places that I've ever been. It was in one of the turrets of the castle, near the top. There is a strong Muslim influence in the designs on the walls; the geometric patterns and the floral designs are typical of Muslim artwork, according to our professors. The decoration wasn't what made this room cool. I know the pictures are blurry, but bear with me.
In between each arc painted on the wall is slight indent in the stone. If someone whispers in to one of the indents, no one else in the room can hear it. Unless, that is, you happen to have your ear pressed to another one of the indents. Then it sounds as if they were speaking directly in to your ear. According to the guide, if you whisper in to the lower indent, the sound carries to indents in the room below. If you stand in the direct center of the room and speak to the ceiling, the sound will echo all around you, but will sound normal to anyone who isn't standing in the center.
Keep in mind, this was constructed sometime in the 1400's. How's that for a medieval marvel?