Why is the Nanjing Himalaya called the Fortress?

Nanjing Himalaya is called a gun tower because its appearance resembles the gun towers in ancient cities, which shows the uniqueness and distinctive features of the architecture. Nanjing, referred to as Ning, was known as Jinling and Jiankang in ancient times. It is the capital of Jiangsu Province, a sub-provincial city, a megacity, and the core city of the Nanjing metropolitan area. Nanjing is located in the southwest of Jiangsu Province and on the lower reaches of the Yangtze River. The city covers an area of ??6587.04 square kilometers. As of 2022, *** has 11 municipal districts, 95 streets, 6 towns, 888 urban communities, 357 rural communities, and a permanent population of 9.4911 million people. In 2022, Nanjing's regional GDP will be 1,690.785 billion yuan. Nanjing is the international shipping and logistics center of the Yangtze River. It is an important gateway city in the country that radiates from the Yangtze River Delta and drives the development of the central and western regions. It is one of the four ancient capitals in China and an important birthplace of Chinese civilization. It has the names of "ancient capital of six dynasties", "city of ten dynasties" and "dragon pan". It is known as "Huju" and has the reputation of "the world's literary hub" and "the first school in the southeast".