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.
Tongchuan is a municipality under the jurisdiction of Shaanxi Province, which is located in the junction zone of central Shaanxi Province, Guanzhong Basin and Northern Shaanxi Plateau, adjacent to Yan'an, Weinan and Xianyang. Tongchuan is a continental monsoon climate with four distinct seasons and obvious monthly changes in air temperature. the area is 3882 square kilometers, and the city has jurisdiction over three districts and one county. In 2017, the city's resident population was 833400. Tongchuan has convenient transportation, which is an important part of the Guanzhong economic belt, and it is a necessary place leading to the Mausoleum of the Yellow Emperor and Yan'an, the holy place of revolution. Tongchuan New area is 68 kilometers away from Xi'an and 72 kilometers away from Xi'an Xianyang International Airport. Xi'an-Huangling Expressway passes through the border, and the two branch railways of Xiantong and Meiqi are connected with the Longhai artery. In 2017, Tongchuan achieved a GDP of 34.859 billion yuan, of which the added value of the primary industry