The Sofia Metro is a rapid transit network serving the Bulgarian capital city Sofia. It is the only metro in Bulgaria. Inaugurated on 28 January 1998, the metro has expanded rapidly to meet the growing demands of the city's residents and visitors. Currently the Sofia Metro consists of four interconnected lines serving 47 stations, with a total route length of 52.0 kilometers and ranks 14th among the top 20 most extensive European metro systems, as of 2023. The system is characterized by its clean and well-maintained stations, many of which display contemporary architectural designs. As one of the youngest metro systems in Europe, Sofia's underground network plays an important role in reducing traffic congestion and increasing the overall accessibility of the city.