Historical Overview-Data
The fate of the Castle of Chios has always been intertwined with the fate of the city and island of Chios, as the Castle has played a major role in the political, military, and economic functions of the island. The Castle which exists in the town today was build around the remains of an older Byzantine castle, evidencing the lasting influence of the site. While the Castle remains in remarkably good condition, especially for its age, it did suffer extensive deconstruction during the refugee crisis of the 1920’s as a result of the Greco-Turkish War in which thousands of Anatolian Greeks took refuge on the island.

The walls form an uneven quadrilateral, which, at each corner, have tall, wide bastions with integrated older towers called torrioni, while the linear parts of the wall are interrupted by smaller bastions and half-bastions. Eight of the original twelve bastions are preserved. The land walls are surrounded by a wide moat, with three gates providing access to both the mainland and the sea. Today, only the Porta Maggiore (main entrance) is preserved in its original state.

The point at which the North West land wall and the Seaside Wall meet sits the Northeast Bastion, usually referred to as the Tower of Antonio Zeno. The bastion features a ring corridor with chambers of artillery-firearms at the moat level. In the center of the fortress lies an integrated tower whose core part forms an older section of the coastal Castle that dates back to the Hellenistic period. Recent excavations within the Castle have confirmed the habitation of the area from the Hellenistic times onward.
The existence of the castle in the Byzantine period is confirmed between the 7th and 9th centuries; this period was characterized by a consolidation of the Byzantine Empire which was faced numerous internal and external threats. From then up to the 14th century, the existence of the city in the same area is confirmed by excavations, while the fortifications were referenced in primary sources.

South Turret
The restoration and alterations to the walls were mostly undertaken during the Genoese era (1346-1466 AD) and from the 15th century onward. The Ottoman occupation of the Castle of Chios (1566-1912 AD) was interrupted by a brief period of Venetian occupation (1694-1695) under the leadership of Admiral Antonio Zeno, for whom the Northeast Bastion is named.
The Seaside Wall
The Seaside Wall, which is the east side of the Castle of Chios, extents between the Northeast Bastion and another lost Bastion at the southeast end, with a total current length of approximately 248m.

Preserved near the Seaside Wall is a Byzantine fountain referred to as the Kyra Bysi (Cold Fountain). While the Venetian admiral Antonio Zeno did not actually construct the Northeast Bastion, he did build the external layer of the Seaside Wall, connecting it with the Northeast by use of two towers-bastions. The Northeast and Southeast walls then formed a larger walkway, called a chemin de ronde, as the void in between the new external and the old internal Seaside walls was filled. This project, although it would prove to be last major modification to the walls of the Castle, would enable the Castle to successfully defend itself from the sea for the first time in its history, as the old internal Seaside Wall had always been a weak-spot.

The Venetian renovations saw much of the old Seaside wall completely dismantled in order to be merged with the new external Seaside wall. The gap between the two walls was filled so as to accommodate the needs of contemporary systems of artillery, as no constructions had been undertaken since the Genoese occupation.
The old inclined retaining wall (called a scarpa) is concealed within the filling between the internal and external walls; some of the original parapets and battlements of the Seaside Wall have recently been restored. These recent excavations have revealed previously concealed sections of the walls as well as confirmed historical traditions regarding the construction phases of the Castle.

New Scientific Evidence
As the project was carried out, the scientific research and restoration works of the Internal Seaside Wall indicated that an older construction phase was undertaken during the Byzantine era, specifically during the 13th century, although these repairs are currently concealed within the newer constructions.
These constructions were carried out during the Genoese occupation of Chios from (1304-1327 A.D.). At the north section of the Internal Seaside Wall, elements of the fortification architecture of contemporary structures of the Genoese occupation, before the use of artillery, are evidenced, for example, by the triangular arrow-slits that were later enclosed by the Venetians. At the north section of the Internal Seaside Wall the square protracted towers of the Byzantine and Genoese era are not preserved, although they are at the south section.

During the Venetian period, the chemin de ronde was filled, and the Wall raised and reinforced with the Internal Wall facing the city, a construction that appears to be designed by the Italian architect Leonardo d’Andria from 1409-1427. The last addition to the Seaside Wall was the construction of the retaining wall at its east external facade. This addition can be attributed to the Italian architect Michelozzo Michelozzi, as part of a program of re-fortification of the Castle of Chios that he had instigated and which was executed from 1464-1471. At the south section the Internal Seaside Wall features almost the same total dimensions as the north but with differences in the preserved phases of construction.