A subway is not just a mode of transportation. It's an intricate system that moves large numbers of people efficiently through urban areas, often operating underground or on elevated tracks above streets. Subways play a crucial role in city infrastructure, helping to reduce traffic congestion and lower air pollution. They also serve as social spaces, economic drivers, and cultural symbols for many cities around the world. Additionally, modern subways incorporate technology for ticketing, tracking, and safety measures. Each subway system is unique, reflecting the history, geography, and needs of its city.