The acropolis is a chalk massif with a cliff face falling into the sea in the south, while the north end narrows to 140 metres wide. The settlement in the form of a massive trapezoid, extended to the north with a large retaining wall in terraces (about eleven metres high) and was surrounded by a wall (repeatedly restored and modified) with an exterior of squared stone blocks and an interior of rough stone ("emplecton"). It had five towers and four gates. To the north, the acropolis was fortified by a counter wall and towers from the beginning of the fourth century BC.