Routes here lean toward the demanding end, so plan full days and watch the forecast. Around 55 percent are circular routes, so parking once is usually an option.

The most reliable season overall is april to june, september to november. Start with Κλασικός Μαραθώνιος Αθηνών or Εθνικό μονοπάτι O22 if you want the highlights without a lot of research.