• The wall body: The Ming Great Wall usually had battlements 1.8 meters (6 feet) high with loopholes and crenels, and parapet walls 1.2 meters (4 feet) high.
• Flanking towers: Every 500 meters or less (1,640 feet) on the Great Wall there was a flanking tower allowing defenders to shoot arrows at attackers at the face of the wall.
• Fortresses were built at important/vulnerable access points (passes), such asShanhai Pass Fortress, Juyong Pass Fortress, and Jiayu Pass Fortress. There were many archery windows and gates on the forts. The fortress gatehouses were the strongest and most impregnable structures on the Great Wall.