The development of underground subway systems has revolutionized urban transportation, providing efficient and sustainable solutions to address the challenges of congestion and mobility in rapidly expanding cities. This research explores the origins, design, and initial safety considerations of the first metropolitan subway system, focusing on the Paris Metro as a pioneering example. Additionally, the research presents two tables that provide a comprehensive overview of the major milestones in the history of underground subway systems and the current state of selected subway networks worldwide. These tables highlight the global spread of subway systems, their impact on urban transportation, and their continuous evolution to meet the growing demands of contemporary cities. The historical milestones demonstrate the visionary ideas of inventors and city planners. The current status of subway systems showcases their scale, significance, and role in shaping urban mobility. The presented information underscores the importance of underground subway systems as vital components of sustainable urban development and emphasizes their ongoing contributions to improving the quality of life for millions of people worldwide.