The Belgrade Metro (Београдски метро/Beogradski metro) is a planned rapid transit system in Belgrade, Serbia currently under construction. The construction of the full metro system has been delayed repeatedly, mostly due to lack of funding. Construction of the first line began on 22 November 2021. Belgrade has a population of around 1.7 million people, making it the largest city by population without a rapid transit system in Europe. Traffic congestion is common and poor infrastructure has put additional strain on the city, while the existing public transport system is incapable of efficiently shuttling passengers even from the suburbs to the downtown and back, let alone from one outlying end of the city to another. At the same time, the suburban railway system BG Voz, which runs underground through the city centre, is only considered to have a role of an S-Train. The construction of a metro is meant to alleviate these problems in the near future. As a result of the decades of misfortune concerning the construction of the metro system, using play-on-words, Belgrade has been jokingly called "half of a metropolis" (in Serbian: "metropolis" – metropola; "subway" – metro; "half" – pola), or the project has been humorously referred to as "Waiting for Metro" (čekajući metroa), which in Serbian rhymes with the title of Samuel Beckett's play Waiting for Godot (Serbian Latin: Čekajući Godoa), in which the titular character actually never arrives. A subway was mentioned for the first time in 1923. It was envisioned by the first urban plan of Belgrade adopted after an international design competition. In 1938 the first three routes were proposed: Bulevar kralja Aleksandra-Zemun, Kalemegdan-Autokomanda and Topčider-Viline Vode (Railway station "Dunav"). The Kalemegdan line was planned to be a touristic line, which would be connected with the regular above-ground tracks and continue to Avala, a mountain outside the city. The plans were abandoned due to the outbreak of World War II.