The Pan-European Picnic was a peace demonstration held on the Austrian-Hungarian border near Sopron, Hungary on 19 August 1989. The opening of the border gate between Austria and Hungary at the Pan-European Picnic was an event in the chain reaction, at the end of which Germany reunified, the Iron Curtain fell apart, and the Eastern Bloc disintegrated. The communist governments and the Warsaw Pact subsequently dissolved, ending the Cold War.
The idea of opening the border at a ceremony and testing the Soviet Union's response came from Ferenc Mészáros of the Hungarian Democratic Forum and Otto von Habsburg, then the President of the Paneuropean Union. The idea was brought up by them to Miklós Németh, then the Hungarian Prime Minister, who also promoted the idea.
Wikipedia https://en.wikipedia.org/wiki/Pan-European_Picnic
Address (Unnamed Road), 9421, Hungary
Coordinates 47°45'23.314" N 16°37'18.238" E