The town boasted a citadel surrounded by an 800-metre wall, built over the last decades of the 5th century BC to ensure the safe passage of Athenian war and commercial ships in the Euboean Gulf. The imposing main gate was situated at the south face of the wall and was supported by towers on either side. Military premises took up the upper part of the citadel, while the lower part included both public and private buildings. Rhamnous may have been a rather secluded area, though it did function as a commercial and military hub, which meant it was guarded throughout the year by Greek or foreign mercenaries, as well as by ephebes (young men) on their second year of compulsory military service. The presence of ephebes there is supported by archaeological evidence and must have contributed greatly to the social life of the city.
A labyrinthine network of primary and secondary roads connects the numerous buildings of the citadel; the main road runs between the south gate, the agora, and the upper military premises.
The shift of power from Athens and Sparta to Macedon was reflected on Rhamnous in the 3rd century BC, when the ephebe soldiers disappeared, and the sporadic occupation of the citadel signalled the Macedonian rule in Attica.