The Budapest Metro () is the rapid transit system in the Hungarian capital Budapest. It is the world's oldest electrified underground railway system, and the second oldest underground railway system with multiple stations, after the originally steam-powered London Underground. Budapest's iconic Line 1 was completed in 1896. The M1 line became an IEEE Milestone due to the radically new innovations in its era: "Among the railway's innovative elements were bidirectional tram cars; electric lighting in the subway stations and tram cars; and an overhead wire structure instead of a third-rail system for power." Since 2002, the M1 line was listed as a UNESCO World Heritage Site. History To clarify where the first "metro" in continental Europe was built, a few distinctions must be made. While the original Metro Line 1 is the oldest electrified underground railway in continental Europe, it is not the oldest underground railway. Outside of the United Kingdom, the oldest fully underground urban railway in the world is the Tünel line in Istanbul, built in 1875. However since Tünel is a funicular railway, it may or may not be considered a "metro" line, in the classic sense. Therefore, depending on one's definition of a metro, the Budapest Metro is either the oldest or 2nd oldest underground urban railway in continental Europe. The original Metro Line 1 ("Földalatti") ran for 5 km from Vörösmarty tér to Széchenyi fürdő (from Hungarian föld "earth, ground", alatt "under"; so "the underground"). Line M1 was inaugurated on May 2, 1896, the year of the millennium (the thousandth anniversary of the arrival of the Magyars), by emperor Franz Joseph. It was named "Franz Joseph Underground Electric Railway Company" (). Works on Metro Line 2 started in the 1950s, although the first section did not open until 1970. It follows an east–west route, connecting the major Keleti (Eastern) and Déli (Southern) railway stations. Planning for Metro Line 3 began in 1963 and construction started in 1970 with help of Soviet specialists. The first section, consisting of six stations, opened in 1976. It was extended to the south in 1980 with five additional stations, and to the north in 1981, 1984, and 1990, with nine additional stations. With a length of approximately and a total of 20 stations, it is the longest line in Budapest. Construction of the fourth Metro line began in 2004. The line opened after several delays and budget overruns in May