Historical background: in 490 BC, the Persian fleet landed in the Bay of Marathon, with 20,000 soldiers set to conquer Athens. General Miltiades implemented a military strategy to rout them. He succeeded and then sent the messenger Pheidippides to announce the good news.
He made the trip without stopping and died of exhaustion just after delivering his message. Herodotus and Plutarch contradict this version, but the race now belongs to posterity and you can follow the blue marked path he took from Athens to Marathon (or vice versa). Going to Marathon is a refreshing break away from the suffocating heat of the big city.
Have lunch at the edge of a lake lined with olive trees, and visit the museum that preserves many pieces of the battle. Lounge between pine forests and beaches and make a gourmet break in one of the little restaurants where you can savour freshly caught fish washed down with Ouzo.