MAYDAY Electronic Music Festival - since 1991. April 30, 2023 7 p.m. - 9 a.m Westfalenhallen Dortmund. One of the longest running electronic music festivals in Europe, Mayday Dortmund has been raving for over 25 years. It attracts huge international techno megastars from around the world and half a million fans since its inception giving it the title: The Mother of all Raves. More Info below.