LONDON, United Kingdom — The iconic London Underground sign, featuring a red circle with a blue bar, marks the entrance to a Tube station. Known as the "roundel," this symbol is a widely recognized emblem of London's public transportation system. The London Underground, commonly referred to as the Tube, is one of the oldest and most extensive subway networks in the world.

Photograph by David Coleman. The London Underground sign, characterized by its distinctive red circle and blue bar, is an enduring symbol of the city's extensive public transportation network. Commonly referred to as the "roundel, " this emblem marks the entrances to Tube stations across London, guiding millions of passengers through the historic and sprawling subway system known as the Tube. Established in 1863, the London Underground is the oldest metro system in the world, comprising 11 lines and serving over 270 stations. The roundel's design has become synonymous with London itself, symbolizing the city's efficient and expansive public transit system. The London Underground not only facilitates daily commutes for residents but also serves as a crucial means of transportation for tourists exploring the city's numerous attractions. The sign's simple yet effective design ensures easy identification and navigation for passengers, contributing to the system's reputation for reliability and convenience. The roundel has undergone various iterations since its inception, reflecting the evolution of the Underground while maintaining its core identity.