The archaeological site of Dystos extends over the Kastri hill, where the imposing ancient city wall stands to this day. The wall, which dates from the first half of the fourth century, is a typical example of Classical defensive architecture. Built mostly of large cut-stone blocks, it is two metres wide and is reinforced perimetrically by eleven towers; the only gate rises in its east section, flanked by two towers. The fine masonry and imposing eastern gate may have saved Dystos from the siege mentionned is Theopompus's Philippica, which has not yet been identified with a specific incident.
On the northwest and south of the hill are the remains of houses built of ashlar blocks during the Archaic and Classical periods (according to their masonry). Local marble was used for their construction, as shown by traces of quarrying near the fortification wall. Most houses had a single room, and some had a courtyard and stable. The best preserved house, the so-called Megali Oikia, or Great House, located east of the settlement, is a fine example of domestic architecture of the fourth century BC. A single main road running north-south provided access to and crossed the fortified settlement, and a number of smaller streets led to the houses. A large rock-hewn public cistern near the south section of the fortification wall supplyied the town with water.
The recent discovery of two stone landmarks provides important evidence on the city limits. The first one dates to the second half of the fifth century BC and was found on the east side of the lake, south-east of the church of Agios Georgios. The second one bears the inscription oros demo (municipality limit); dated to the fourth century BC, it was carved on a rock inside the enclosure of a two-storey building on Kontostauleikon hill. This inscription proves that Dystos was a municipality located within the boundaries of Eretria. The discovery of ancient buildings, architectural parts, graves, and funerary reliefs in the plain of Dystos demonstrates that occupation extended into this area, too.