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.
Yijun County, which belongs to Tongchuan City, Shaanxi Province, is located in the middle of Shaanxi Province, in the north of Tongchuan City, and at the junction of Guanzhong Plain and Northern Shaanxi Loess Plateau. The county seat is 120km south from the provincial capital Xi'an and 27km north from the Huangdi Mausoleum of Xuanyuan, with a total area of 1531 square kilometers. National Highway 210 and Tonghuang first-class highway pass through the border, known as the "flyover from Guanzhong to northern Shaanxi". Yijun County is not only named because of Yijun water, but also because it is suitable for kings to spend the summer. There are Yangshao cultural sites, Pengzu hometown, Northern Wei grottoes, Jiangnu tear Spring, Yunmeng Mountain Taoist resort, the warring States and Wei Great Wall, among which Yijun and the warring States Wei Great Wall was included in the World Cultural Heritage list of the Great Wall of China. As of 2018, Yijun County has jurisdiction over 1 street, 6 towns and 1 township. In 2017, the resident population of Yijun County was 92100.