The battle of Marathon was not fought where the modern town stands. It was fought on the coastal plain, and Schinias is the northeastern end of that plain. The Persian fleet anchored in this bay in 490 BC, and the army camped on the flat ground behind this beach.

The wetland here was called the Great Marsh, and it decided the battle. Pausanias wrote that the Persians, retreating and not knowing the ground, pushed one another into it, and that this was where most of them died. The same scene was painted at the centre of the Marathon picture in the Stoa Poikile in Athens.

The marsh covered most of the northeastern plain until it was drained in the twentieth century. What survives inside the park is only a part of it.

The Athenians set up a victory monument of white stone near the western edge of that marsh, beside the chapel of Mesosporitissa. Several modern scholars think the position of this monument, rather than the burial mound, shows best where the fighting actually took place.

The mound itself — the tomb of the 192 Athenian dead — stands further out in the plain, and the finds from the battle are in the museum at Marathon.

The park covers just under fourteen square kilometres, and it contains an unusual number of different habitats — nineteen, according to the Natura 2000 survey.

The forest

The forest behind the beach is the rarest part of the park. It is a coastal wood of Aleppo pine and stone pine, growing straight out of sand. Very few of these survive in Greece, or anywhere in the Mediterranean. It is also what gives the beach its shade.

Marked paths run through the trees. The ground is flat and easy — this is walking, not hiking.

The marsh

Inland lies the Great Marsh, the largest wetland in Attica, fed by the Makaria spring. It is made up of reed beds, rush beds and salt marsh.

More than two hundred species of bird have been recorded here, and the park is a real stopping point on the spring and autumn migrations. Herons, egrets, ducks, waders and glossy ibis are the most common. Orchids grow in the wet ground in spring.

The peninsula

At the eastern end, the Kynosoura peninsula — the name means dog's tail — is dry limestone scrub, almost untouched, with a rare fritillary flower growing among the rocks.

Schinias is one long beach rather than several. It follows the curve of the bay, and it is the reason most people come.

The sand is fine and pale, and the water stays shallow and warm a long way out. Along much of the beach the pine forest comes down to the back of the sand, which means there is real shade without renting anything.

In practice the beach has three parts. The northern end, near the rowing centre, is the quietest and the most natural, and the trees come closest to the water. The middle section has the beach bars — organised, but not overbuilt. The southern end catches the wind and is used for board sports.

Between the bars, footpaths lead through to open stretches of sand. This is worth knowing, because from the road it can look as though there is no way down to the beach.

The Olympic Rowing and Canoeing Centre was built at the northern edge of the park for the 2004 Games, on a course 2,250 metres long cut into the marsh. It is still used for national and international competitions, rather than standing empty. It is also why the roads and open spaces here feel different from a normal Greek beach.

The southern end of the bay gets steady wind from the Aegean, and windsurfing and kitesurfing have been established there for a long time. In season you can rent equipment and take lessons on the sand. Southerly winds in winter bring kitesurfers out when the beach is otherwise empty.

The flat ground through the forest and along the coast is also good for easy cycling.