The Greek Adranon, to which the modern built-up area was superimposed, obliterating its memory for a long time and making the archaeological investigation extremely difficult, was equipped with a solid wall built with a double face of lava ashlars with internal sack filling with small stones and land. The walls are conventionally defined "Dionigian walls", wanting to attribute the construction to the first plant of the city, founded by the will of Dionysius I in 400 BC, but it would be more correct to call them "Greek" or "ancient" walls in how much it is not possible, at the current state of the investigations, to indicate exactly the dating.
For the construction system, for the presence of quadrangular towers and for positioning them, for the materials found, they must be framed chronologically between the IV and III century BC They adapted to the morphology of the terrain and were presumed to have a length of 5 kilometers but only some sections, in addition to that of the Defense district and the tower of the church of S. Francesco, were identified, severely compromised by destruction and unauthorized age modern.
Already in 1781 the prince of Biscari, a passionate Catania scholar and archaeologist ante litteram, had known and described them in the Journey for all the antiquities of Sicily. Stopped on paper in Jean Houel's drawings, they are remembered by local historians (Giovanni Sangiorgio Mazza and Salvatore Petronio Russo). With the excavations of Paolo Orsi, at the beginning of the 1900s, the walls were brought back into view for a length of four hundred meters in the Defense district, two posts were identified and the keep was freed close to the church of San Francesco. Placed under protection by the Superintendence of Syracuse of Luigi Bernabò Brea shortly after the middle of the last century, they returned to being the subject of regular excavations conducted by the Superintendence for Cultural and Environmental Heritage of Catania in the years 2007-2008 and, finally, open to the public for a while and equipped with an antiquarium and didactic room.