Greeks gathered at the Polytechnic University in Athens on Tuesday to commemorate the anniversary of the 1973 student uprising against the military dictatorship.
People laid flowers at the memorial and the gate destroyed by a tank during the crackdown.
Annual marches to the US Embassy were held under heavy security, with major roads closed and subway stations shut.
The 1973 protests, in which at least 20 people are believed to have been killed, remain a defining moment in Greece’s struggle for democracy.