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.
Shuangyashan City is a prefecture-level city in Heilongjiang Province. Shuangyashan City is located in the northeast of Heilongjiang Province, with high terrain in the southwest and low in the northeast, and is located in the humid climate zone of the middle temperate zone. It has jurisdiction over 4 districts and 4 counties, with a total area of 22483 square kilometers and a total population of 1.423 million in 2017. Within 300 kilometers of Shuangyashan, there are Tongjiang, Fuyuan and other first-class ports to Russia, which are located in the core area where Heilongjiang Province opens to the Russian far East, and is an important node city for the construction of the "China-Mongolia-Russia Economic Corridor." It has a first-class national port-Raohe Port, the Raohe Sino-Russian Exchange Trade Zone and the Sida Sino-Russian International Trade Center have been put into operation, and the Sino-Russian International Cultural Logistics Economic and Trade Industrial Park is being constructed. to build an import and export processing base for Russia and a national trade distribution base for Russia. Successively opened Shuangyashan to Haba.