Perhaps one of the most recognizable subway systems in the world, London’s Underground is 249 miles of public transit, much of which is hidden beneath the world-famous city.

Affectionately known as "the Tube" this public transportation system has 11 different subway lines and serves 270 subway stops and serves 1.37 billion people a year, making it one of the biggest subway systems in the world. By comparison, New York City’s subway system has 36 lines, 472 stations, and 1.76 billion annual riders.

The history of London’s mass transit system dates back to the mid-1800s with the construction and subsequent opening of the Metropolitan Railway, the world’s first underground railway. Originally a system using wooden carriages pulled by large steam engines, the Underground quickly transformed and expanded with the 1st deep-level tube line opening in 1890.

By the early 1900s, the Underground had begun to operate electrically and the iconic UNDERGROUND signs appeared outside subway stations around London, according to Slate. During both world wars, London’s subway system was used as shelters during air raids. Post-wars, the massive system continued to expand farther outside central London.

And, with an ambitious 2020 vision for the Underground, it’s safe to say this renowned subway system will continue to expand to serve the millions of daily riders.

So, when in London, do what the Londoners do. I took a ride on the oldest subway system in the world — and it was honestly pretty wonderful.