The Helsinki Metro system serves the area of Helsinki and southern Espoo.
The Helsinki Metro began operation in 1982, and the first part of the extension to Espoo was opened in November 2017, and the second part opened in December 2022.
The Helsinki Metro is the northernmost metro in the world.
The Helsinki metro consists of two lines (M1 and M2) and 30 stations. M1 terminuses are Kivenlahti and Vuosaari. M2 terminuses are Tapiola and Mellunmäki.
All the stations from Kivenlahti to Sörnäinen are underground, and stations to the east of Sörnäinen are all above ground.
Koivusaari station is the only metro station in the world located under the sea.
It's only allowed to enter the platform area with a valid ticket, although it's possible to access it without a ticket inspection.