The initial motion for building a metropolitan railway system in Helsinki was made in September 1955, though during the five decades beforehand, the idea of a tunneled urban railway for Helsinki had surfaced several times.
Gerakan awal untuk membangun sistem kereta api dalam kota di Helsinki dibangun pada September 1955, meskipun selama lima dekade sebelumnya rencana pembangunan terowongan kereta api dalam kota bagi Helsinki telah muncul beberapa kali.