London Underground. The London Underground is the oldest underground railway in the world, and it is also one of the busiest. The network has 11 lines and 272 stations, and it carries over 4 million passengers every day.
New York City Subway. The New York City Subway is the largest underground railway system in the world, with 24 lines and 472 stations. The system carries over 6 million passengers every day.
Paris Métro. The Paris Métro is the oldest underground railway system in continental Europe, and it is also one of the busiest. The network has 16 lines and 302 stations, and it carries over 5 million passengers every day.
Shanghai Metro. The Shanghai Metro is the longest underground railway system in the world, with 17 lines and 863 stations. The system carries over 2.8 million passengers every day.
Beijing Subway. The Beijing Subway is the second longest underground railway system in China, and it is also one of the busiest. The network has 19 lines and 374 stations, and it carries over 10 million passengers every day.
Tokyo Metro. The Tokyo Metro is one of the busiest underground railway systems in the world, and it is also one of the most technologically advanced. The network has 13 lines and 277 stations, and it carries over 8 million passengers every day.
Mexico City Metro. The Mexico City Metro is the second longest underground railway system in North America, and it is also one of the busiest. The network has 12 lines and 195 stations, and it carries over 4.5 million passengers every day.
São Paulo Metro. The São Paulo Metro is the largest underground railway system in South America, and it is also one of the busiest. The network has 4 lines and 64 stations, and it carries over 4 million passengers every day.
Seoul Metro. The Seoul Metro is one of the most technologically advanced underground railway systems in the world, and it is also one of the busiest. The network has 9 lines and 285 stations, and it carries over 8 million passengers every day.