Finland was compelled to rent the peninsular to the former Soviet Union at the end of the continuation war in 1944 for a period of 50 years.
Located some 40 kilometres west of Helsinki, it was described by some as Stalin's dagger pointing at the Finnish capital.
The area includes the municipalities of Deferby, most of Kirkkonummi, Porkkalanniemi, Upinniemi and several small islands.
Porkkala was returned to Finnish sovereignty by Nikita Khrushchev on January, 26, 1956. The peninsula’s military significance had diminished and was expensive for Moscow to maintain. Porkkala’s return was seen by some observers as a sign of Soviet peaceful intentions. In the same year, though, Soviet forces crushed the Hungarian revolution.