Budapest Metro

Your fellow passengers accompanying you to your destination murmur their own conversations and listen to music and sleep. A metro, or rapid transit, underground, subway, elevated railway, metro or metropolitan railway system, is a passenger transport system in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on elevated viaducts above street level. Outside urban centers, rapid transit lines may run on grade separated ground level tracks. The first rapid transit system was the London Underground, which opened in 1863. The technology quickly spread to other cities in Europe, and then to the United States where a number of elevated systems were built. At first these systems used steam locomotives, with the term later coming to entirely mean electric systems.