Fortress of Fyli. Municipality of Fyli
Fortification work of the 4th century B.C. which controls the mountain pass between Attica and Viotia. It is located about 1000m. southwest of the place where the ancient municipality of Fyle is located.
The Fortress has an irregular elliptical plan and dimensions 95x30m. The wall is built with the isodomic system and surrounds the north, south and east side of the hill, while the steep west and southwest side remained unwalled. In some places it is preserved at a height of sixteen (16) structures. The main gate is to the east and has collapsed. The southern smallest gate with its lintel is preserved.
The fortress has four imposing towers (three rectangular and one circular) that protrude far from the outer line of the wall. The most voluminous of all is the circular one, with a diameter of 6m, which protected the smooth and vulnerable north side.
Inside the fortress there are ruins of a few buildings, for the residence of the guard.