The ancient fortress of Phyle is located on the northwest slope of Mount Parnes, at an altitude of 850 m, and about 10 km to the northwest of the modern settlement of Phyle. Its construction dates from the 4th century. It occupies a strategic location, as it is situated on the most direct, though definitely not the easiest, road connecting Athens with Thebes. The fortification is of irregular plan featuring four towers; it was constructed of wellhewn rectangular blocks of local grey limestone. The fortress of Phyle is mentioned on 4th century inscriptions and decrees. It was systematically in the war against the Macedonians, which took place in the 3rd century. Between 304 and 283 the fortress was occupied by Cassander, during his conflict with Demetrius I. The latest related epigraphic evidence dates from 236 and is associated with repairs.