Introduction to the first level: The city of Shanhaiguan is a small city with a circumference of about 4 kilometers. The entire city is connected to the Great Wall, with the city as a gateway. The city is 14 meters high and 7 meters thick. The city has four main gates and a variety of ancient defensive buildings. It is a city gate with a relatively complete defense system and is known as "the first gate in the world". The first pass takes the mighty and majestic "The First Pass in the World" Arrow Tower as the main body, supplemented by Jingbian Tower, Linlu Tower, Muying Tower, Weiyuan Hall, Wengcheng, Dongluo City, Great Wall Museum and other Great Wall buildings to show tourists It represents the ancient Chinese city defense architectural style.