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.
Mado, which means "the source of the Yellow River" in Tibetan, is located in the northwest of Guoluo Tibetan Autonomous Prefecture in Qinghai Province, in the south of Qinghai Province, in the northwest of Guoluo Tibetan Autonomous Prefecture, and belongs to Guoluo Tibetan Autonomous Prefecture. Mado County is bordered by Dulan County, Haixi Mongolian Autonomous Prefecture in the north, Xinghai County in Hainan Tibetan Autonomous Prefecture and Maqin County in Guoluo Tibetan Autonomous Prefecture in the east, Dari County in Guoluo Tibetan Autonomous Prefecture and Shiqu County in Sichuan Province in the south, Qumalai County in Yushu Tibetan Autonomous County in the west, and Yushu Tibetan Autonomous Prefecture in the southwest. It is 207km wide from north to south and 228km long from east to west, with a total area of 25253 square kilometers. The average altitude is more than 4200 meters, and the annual average temperature is-4 ℃, which belongs to alpine steppe climate. Lake Eling, Lake Zaling, Lake Donggezona, Xingjinghai,