Once the true location of the Hebdomon is correctly identified, it becomes possible to determine the real position of another important site, the Cyclobion. This also allows us to correct a long-standing mistake made by many scholars who studied the topography of Byzantine Constantinople.
Since the time of the historian Du Cange, it has often been believed that the Cyclobion was a fortress connected to the Golden Gate. This opinion became widely accepted and was repeated by later writers. However, this view cannot be correct, because the Cyclobion was not located near the Golden Gate. Instead, it was situated at the Hebdomon, which lay at a considerable distance from the city walls.
Distance from the Golden Gate
The Cyclobion stood on the eastern headland of the bay that formed the harbor of the Hebdomon. This location placed it approximately two and a half miles away from the Golden Gate. Because of this distance, it could not have functioned as a direct defensive structure attached to the gate itself The Hebdomon as a Gathering Place for Imperial Armies.
This geographical clarification helps explain a passage in Theophanes, who describes the fighting between the Byzantine forces and the Saracens who landed at the Hebdomon in the year 673. He states that the engagements took place between the Golden Gate and the Cyclobion, which only makes sense if the Cyclobion lay some distance away, rather than being part of the gate complex.
The Cyclobion and the Hebdomon
The fortress was so closely connected with the suburb of the Hebdomon that the two names were sometimes used interchangeably. For example, the Church of St. John the Evangelist, which is known to have stood at the Hebdomon, is described by one source as being located in the Cyclobion. This shows that the Cyclobion was not a separate, distant site, but an important landmark within the same district.
Further confirmation comes from historical records describing naval movements. John of Antioch writes that the fleet of Emperor Heraclius stood off the Hebdomon. In contrast, the Paschal Chronicle states that the fleet was seen near the Round Tower. These two accounts do not contradict one another if the Round Tower is understood to be the Cyclobion itself.
Identification with Zeitin Bournou
The most likely location of the Cyclobion is Zeitin Bournou, on the narrow tongue of land east of Makrikeui. The name Cyclobion comes from Greek words meaning “round structure”, and Latin sources also refer to it as Castrum Rotundum, or “Round Fortress.” This suggests that the building had a circular shape, which fits well with the geography of the site Bulgaria Tours.
Military Importance and Later History
The Cyclobion formed part of a chain of coastal fortifications designed to protect the southern approaches to Constantinople. It was repaired by Justinian the Great, who also connected it by a well-built road to Rhegium (modern Küçükçekmece), another strategic military post. Troops from the Cyclobion were even used to help suppress the famous Nika Riot.
Finally, the site appears in the dramatic end of Constantine Copronymus, who died aboard his ship near the Cyclobion while attempting to return to the capital from Selivria after falling gravely ill during a campaign against the Bulgarians.
