The third and final stage of the Conference on Security and Co-operation in Europe (CSCE) - the signing of the Helsinki Final Act - took place in the Finnish capital from 30 July to 1 August 1975.
Thirty-five Heads of State or Government from all over Europe, the USA and Canada gathered for the signing. Among them were the leaders of the two superpowers, Gerald Ford and Leonid Brezhnev, and the two Germanys, Helmut Schmidt and Erich Honecker.
In his speech, US President Gerald Ford underlined the historic significance of the event: "History will judge this Conference not by what we say here today, but by what we do tomorrow - not by the promises we make, but by the promises we keep."
Soviet leader Leonid Brezhnev noted that the prolonged negotiations over the content of the Helsinki Final Act in Geneva had produced "neither victors nor vanquished, neither winners nor losers. It has been a victory of reason.
"Everyone has won: the countries of East and West, the peoples of socialist and capitalist States, whether parties to alliances or neutral, whether large or small. It has been a gain for all who cherish peace and security on our planet."
West German Chancellor Helmut Schmidt was clear about his desire to one day see the two Germanys reunited: "Frontiers are inviolable, but one must be able to change them by peaceful means and agreement.
"It remains our aim to work for a state of peace in Europe in which the German nation will regain its unity through free self-determination."
His East German counterpart Erich Honecker, however, warned: "The terrible wars which devastated our continent in this century were the result of policies which, no matter under what pretext, started from the violation of existing frontiers, from disregard for the sovereignty and territorial integrity of other States."
The Helsinki Final Act encompasses three main sets of recommendations, which are often referred to as 'baskets'. These three baskets are:
The first of the Final Act's three baskets outlines ten principles guiding relations between the participating States. These principles, known as the 'Helsinki Decalogue', are as follows:
The full list of signatories of the Helsinki Final Act is as follows: Austria, Belgium, Bulgaria, Canada, Cyprus, Czechoslovakia, Denmark, Finland, France, the German Democratic Republic, the Federal Republic of Germany, Greece, the Holy See, Hungary, Iceland, Ireland, Italy, Liechtenstein, Luxembourg, Malta, Monaco, the Netherlands, Norway, Poland, Portugal, Romania, San Marino, Spain, Sweden, Switzerland, Turkey, the Soviet Union, the United Kingdom, the USA and Yugoslavia.
In an interesting historical footnote on Helsinki, Finnish Foreign Ministry official Mikko Pyhälä, who preserved the notes scribbled by the 35 world leaders during the summit, made them public in 2005.
"Now that 30 years are gone I thought that it might be a good idea to put them forward. They do reveal something about psychology and culture," Pyhälä told Finnish newspaper Helsingin Sanomat.