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.
Jiuquan, a prefecture-level city of Gansu Province, is located between Altun Mountain, Qilian Mountain and Mazong Mountain at the western end of Hexi Corridor in the northwest of Gansu Province, between latitude 38 °09 "42 °48" north and longitude 92 °20 "100 °20'E. it has been the traffic fortress of the Central Plains and the northeast leading to Xinjiang and the western region since ancient times. In the north, except for a small part of Mongolia, most of it is connected with Alashan League in Inner Mongolia and Xinjiang Uygur Autonomous region to the west. The southern boundary of Qinghai Haixi Mongolian Autonomous Prefecture and Haibei Tibetan Autonomous Prefecture is adjacent to Zhangye City in the east, with a total area of 192000 square kilometers, accounting for 42% of the area of Gansu Province. Jiuquan is one of the four counties in Hexi in the Han Dynasty and an important town of the Silk Road. The terrain is high in the south and low in the north, tilting from southwest to northeast, Qilian main peak from east to west, Gaolai Mountain,