The article is aimed at presenting the topography and the architecture of the ancient town of Parthicopolis located underneath the modern town of Sandanski. The author accepts the assumption of Louis and Jeanne Robert, who believe that this town is the ancient town of Parthicopolis mentioned by the written sources. This hypothesis is supported by new information about the historical geography of the Middle Strymon valley. A suggestion is made about the time of the establishment of the central part of the town based on available epigraphic evidence. The author makes an attempt to trace out the route of the defensive wall enclosing ca. 20 hectares large area. The theatre is the only excavated public building within the later defensive walls dated back to this period. There is information about other buildings situated underneath basilicas № 1 and № 4. Outside the town walls there was a sanctuary and a temple of the Thracian Horseman called Θεὸς Σαληνος. The locations of the Roman graves on the map provide information about the functioning of a large cemetery situated to the south and another one situated on a hill, to the west of the town.