San Diego (/ˌsæn diˈeɪɡoʊ/ SAN dee-AY-goh, Spanish: [san ˈdjeɣo]; Spanish for 'Saint Didacus') is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States and the seat of San Diego County, the fifth most populous county in the United States, with 3,338,330 estimated residents as of 2019. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center. San Diego is the second largest city in the state of California, after Los Angeles.
Tieshan District, located in the west of Huangshi City, Hubei Province, is rich in mineral resources and is named for its rich iron ore. More than 1700 years ago, the ancestors dug and smelted here. Dongfangshuo studied here in the Han Dynasty; Yue Fei, a national hero, forged the "sword of Daye" here; at the end of the Qing Dynasty, Zhang Zhidong, governor of Huguang, built China's first large-scale open-pit iron ore, Daye Iron Mine, which was the largest in East Asia at that time. Tieshan became the cradle of China's modern iron and steel industry. Tieshan District Railway connects Beijing-Guangzhou and Beijing-Kowloon two major transport arteries, and National Highway 106 runs through the whole territory. Tourist attractions include Yellowstone National Mining Park, Luzhangshan Park, Tieshan Temple, Huazang Temple and so on. During the 12th five-year Plan period, Tieshan will invest 20 billion yuan to build the "Iron City of the World".