The Tehran Metro is a rapid transit system serving Tehran, the capital of Iran. It is the largest metro system in the Middle East. Inaugurated in 1999, it has become one of the busiest and most extensive metro systems in the Middle East. It consists of six operational metro lines, with construction work underway on four lines including the northwest extension of Line 4, the south extension Line 6, the north and east extension Line 7 and Line 10. As an integral part of Tehran's urban fabric, the Metro plays a key role in shaping the city's economic growth and accessibility, while ongoing expansion projects underline its continued importance in the future.