Shanghai Metro celebrated its 30th anniversary on Sunday. The city's first Metro line, the 6.6-kilometer southern part of Line 1, which ran between Xujiahui and Jinjiang Park, began operations on May 28, 1993. Meanwhile, the overall length of the city's Metro network, has increased to 831 kilometers, becoming the largest metro system among all the cities in the world, according to Shanghai's Metro operator, Shanghai Shentong Metro Group.A 30-year anniversary ceremony was held at Shanghai Metro's Meilong Base on Laohumin Road in Xuhui District, where the first group of Metro trains stop. Construction of the east part of Metro Line 13 also began on Sunday and the digital operation and maintenance center just completed was officially unveiled.Relying on the Internet of Things and AI analysis technology, this system can monitor the vehicle status in real time, and change the treatment after the failure to the discovery before the failure.The earliest builders are all gray-haired. Seeing the achievements of Shanghai Metro today, they all fell surprised.Few people know that in the 1950s and 1960s, some foreign experts asserted that Shanghai's geological structure, abundant water systems, and soft soil made it impossible to build a fast subway. However, under the persevering experiments, innovations and changes of generations of subway builders, Shanghai has achieved a breakthrough in shield technology, completing the mission impossible.On Sunday, the veterans who once struggled in the front line met the successors of the Shanghai Metro.After 30 years development, the city's Metro system has expanded from five stops to 508 stops, from one line to 20 lines, with passenger capacity from 1.06 million per year to more than 13 million per day.