Aerial view of the acropolis from the north.
The fortification was built in the mycenaean period, probably around 1300 B.C., in the so-called cyclopean manner (making use of large limestone blocks) and was protecting the hill on its three sides, the fourth being naturally protected by the cliff and the lagoon. The wall is 250m. long and 4.5-5.5m. thick, with an average surviving height of ca. 8.4m. Access to the inside of the citadel was provided by three gates, one at each side of the wall, the main gate at the southeastern side being further protected by a gate tower. House ruins belonging to successive habitation phases have come to light inside the acropolis, proving the intensive use of the site during the mycenaean period (1680-1040 B.C.). Human occupation of the site has been verified for phases prior to the fortificationís construction, as early as the Final Neolithic period (ca. 3500 B.C.) and more intensively during the Early and Middle Helladic periods (ca. 3000-1680 B.C.).

In historical times human activity at Teichos Dymaion was, more or less, continuous. During the war between the Achaean and the Aitolian Leagues (220-217 B.C.) the site was seized by the Aitolian general Eutichidas and was later taken without battle by king Philip V of Macedonia, who subsequently handed it to the Dymaians. In roman times the acropolis was part of the Colonia Iulia Augusta Dumaeorum (the imperial colony of Dyme) and was probably inhabited by roman settlers.

Intensive use of the site continued during the byzantine era. Significant alterations to the citadelís original form took place during the middle byzantine period (10th - 12th cent. A.D.): a cross wall, dividing the acropolis in two parts, was built at that time, along with a tower over the southeastern corner of the fortification; the middle gate was disused and blocked by a wall.

The Venetians took over the acropolis in 1408, when the catholic bishop of Patra leased the barony of Patra to them for a five-year period. Later on (1687-1715), 1000 settlers from Lidhoriki (a mountainous town in Phokis, in central Greece) came to live in the surrounding area that was then uninhabited; this is probably the period during which the northern part of the acropolis was used as a cemetery. After that, habitation on the site was very sporadic and has left no traces. When a number of western European travelers visited Teichos Dymaion during the 19th cent. it was found deserted.

More recently, during World War II, the site was used as a military camp by the Italian occupation troops that built a number of installations (gun-shelters, bunkers, storage rooms, dormitories etc), thus causing extensive and irreversible damages to the prehistoric fortification.
6th Ephorate of Prehistoric and Classical Antiquities
From Neolithic times into Late Helladic period.
Hellenistic and Roman periods.
From the Middle Byzantine into the Venetian period.