Olympiakos v Panathinaikos, the eternal rivalry

Sports tell us many entertaining stories. They tell us about fierce rivalries between teams of the same country, the same region and even the same city. Football in particular is renowned for its involving derbies in different parts of the globe. You have Chivas Guadalajara-Club América in Mexico, or Boca Juniors-River Plate in Argentina, or Lazio-Rome in Italy, or Barcelona-Real Madrid in Spain. Perhaps, two areas gain most of the attention for their passionate and, sometimes, violent clashes; one is Latin America, the other is the Balkans.