THE world's first metro, now the world's oldest system, is the London Underground in England, which is more commonly known as the Tube, which was opened in 1863. At 402 kilometers in length the London Underground is also the world's second longest metro system.

The city with the oldest functioning underground railway (subway) line in the world is London. The Metropolitan Railway, which is now part of the London Underground (the "Tube"), opened on January 10, 1863. It originally ran between Paddington (then called Bishop's Road) and Farringdon Street using steam locomotives to pull wooden carriages. While the locomotives were later electrified, the route remains a core part of the modern network today. It is important to distinguish this from the "first underground electric railway," which was the City and South London Railway (now part of the Northern Line), opened in 1890. While other cities like Budapest (1896), Glasgow (1896), and Paris (1900) followed shortly after, London’s 1863 debut marked the birth of rapid transit. Today, the London Underground spans over 250 miles and 272 stations, serving as the historical blueprint for every other subway system in the world. The preserved Victorian-era tunnels are still in use, a testament to the incredible engineering of the mid-19th century.