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.
Haixi Mongolian and Tibetan Autonomous Prefecture, Qinghai Autonomous Prefecture, referred to as Haixi Prefecture, is located in the north of the Qinghai-Tibet Plateau and the west of Qinghai Province, with high terrain in the northwest and low in the southeast, which is a typical alpine and dry continental climate zone; the state has a total area of 300700 square kilometers and has jurisdiction over 3 county-level cities, 3 counties and 1 administrative region; in 2017, the resident population is 515200. Haixi Mongolian and Tibetan Autonomous Prefecture is the Qudi of the Qinghai-Tibet Plateau, with Tibet in the south, Gansu in the north and Xinjiang in the west. It is at the center of the confluence of the four provinces and regions of Qinghai, Gansu and New Tibet, and was once the auxiliary road of the ancient "Silk Road" leading to the Western region. Lanxila optical cable, Qingxin optical cable, Qinghai-Tibet 750 kV AC / DC interconnection line run through the whole territory, Golmud-Lhasa product oil pipeline and Xianning-Lanlan gas pipeline are distributed, Qinghai-Tibet railway and national highway.