The M4 or "Blue Line" is the new Milan metro line, an engineering project that is essential for developing the Lombardy capital and strengthening its position in Europe. Milan’s M4 runs under the city from east to west, passing through the historic centre and reaching Linate airport. From its two terminals, Linate and San Cristoforo, the Milan M4 line is 15 km long with 21 stations. Travelling between these two stations it only takes 30 minutes, and only 12 minutes from Linate Airport to the city centre.