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.
Qinghai Province, referred to as "Qing", is the provincial administrative region of the people's Republic of China and the capital of Xining. Located in the inland of northwest China, Qinghai is bounded by 31 °36 degrees north latitude, 39 °19 degrees north latitude, 89 °35 degrees east longitude, 103 °04 degrees east longitude, Gansu in the north and east, Xinjiang in the northwest, Tibet in the south and southwest, and Sichuan in the southeast. The overall topography of Qinghai Province is high in the west and low in the east, high in the north and south, low in the middle, high and steep in the west, tilting to the east, showing a ladder-shaped decline, and the eastern region is a transitional zone from the Qinghai-Tibet Plateau to the Loess Plateau, with complex topography and diverse landforms. The landforms of Qinghai Province are complex and diverse. More than 4/5 of the areas are plateaus, mountainous in the east and plateaus and basins in the west, with three landforms of the Qinghai-Tibet Plateau, inland arid basins and the Loess Plateau.