In the ruins of Byzantine Gratianoupolis
In the northwest of the settlement of Gratini, on the southern foothills of Rodopi, the ruins of a castle, parts of the fortified enclosure and a chapel are preserved. The height of the castle is about 4 m high and on the eastern side of the walls it has a circular tower. The castle was identified with Gratianoupolis, perhaps associated with the Roman emperor Gratianus (367-383). Written sources give the existence of the city from the 5th century AD and its development in the 13th and especially the 14th century. It was during this period that neighboring Mosynopolis was abandoned after its destruction in 1206 and intense conflicts in the Byzantine Empire over the claim to the throne between the two families of Kantakouzenos and Palaeologos were recorded. In 1361 it was conquered by the Ottomans.
Access to the castle is difficult.