At 10:15 a.m. on December 27, 2025, Jinan Metro Line 4, the eastern section of Line 6, and Line 8 opened and began operation simultaneously, marking a key step for Jinan's rail transit from a "line-network skeleton" toward "networked operation," and the Spring City of Jinan has since entered a true "metro era." Line 4 runs east-west through the main urban area, the eastern section of Line 6 connects core commercial districts with residential areas, and Line 8 opens a rapid corridor between the main urban area and Zhangqiu District. Together with the existing Lines 1, 2, and 3, the six lines complement and interconnect, fully covering commuting, shopping, travel, and other needs. Line 4 in particular is Jinan's first metro line close to the Baotu Spring cluster, known as "Number One Spring Under Heaven," with its nearest point only 1.4 kilometers from Baotu Spring. This "underground artery" running along Jingshi Road has a total length of 40.3 kilometers and 33 stations, linking five core districts—Huaiyin, Shizhong, Lixia, Licheng, and Gaoxin—and filling the gap of no metro service along Jingshi Road.

     As the capital of Shandong, a major coastal economic province, Jinan is the 38th city in China to build a metro and the last sub-provincial city in the country to do so, with construction only officially starting in July 2015. The reason Jinan's metro construction started so late lies neither in its economic scale nor its population size, but in the springs that have made the city famous. Its exceptional spring resources posed enormous challenges to metro construction. How to build a metro beneath ground densely veined with springs without damaging the spring veins is an engineering problem for which there was no successful experience anywhere in the world to draw on.

      Since its founding, Jinan Rail Transit Group, which undertook this arduous task, has unhesitatingly embarked on a pioneering path to solve a world-class problem. To carry out the work at a high level and from a high starting point, the person in charge of the Line 4 project at Jinan Rail Transit Group Construction Investment Co., Ltd. established an academician and postdoctoral workstation and formed a spring-protection innovation studio to conduct scientific and technological research. They collected and organized more than 2,000 sets and over 300,000 items of data spanning more than 60 years across the city. To verify the accuracy of the data, they measured Jinan on foot and touched the spring veins with exploratory boreholes, drilling more than 30,000 holes in every corner of the Spring City, and finally clarified the origins of the springs. Through concentrated efforts, they pioneered an integrated device for foundation-pit dewatering and recharge, achieving a dynamic balance between dewatering and recharge.