This photo shows one of the 4,500 visitors at CERN’s Open Day on 15 September 1984. The festivities, which marked the Organization’s 30^th anniversary, also included a concert and a formal ceremony on 21 September.  CERN’s team of historians put together an exhibition of archival documents, and a history seminar traced over three decades of achievement. Read all about the events in the November 1984 CERN Courier, or browse through the exhibition catalogue and official speeches here.