The Castle of Chios has an area range of 180.000 square meters and its walls “hug” the whole residential complex, with 650 residents. The residence itself inside the Castle’s areas is said to have started at least from the Hellenistic years. Excavation findings certify the existence of the continuation of the residence in the Roman and Early Byzantium years. Temples of the mid Byzantium years certified from sources (10th century) and from excavation findings (11th century). Today’s Castle of Chios is identified with the known from the sources stronghold, which the Genovese ruler of Chios Martino Zaccaria started to build in 1328. In 1329 the castle was taken in account for the Byzantine emperor by Androniko Palaiologo the Third and it remained in the hands of the Byzantine Empire until 1346, so Chios was received as a possession from the Democracy of Genoa. From the year that the Genovese Simone Vignoso occupied the island starts period of the Genovese rule for two centuries, from 1346 to 1566. In the medieval years the Castle of Chios (or Civitas Chii) was the center of political and military administration of Chios. Outside of the walls of the Castle, extended the city, the “borgo”. The island’s governing was managed by a commercial company, Manoa, in which her members from 1362 and on belonged to the faction (Albergo) of Ioustiniani (Giustiniani) in Genoa, ever since then they had the last name of Ioustiniani. In 1566 the pasha Piali occupied the Castle without a fight by order of Ottoman Sultan Souleiman the Magnificent. In 1694 the Castle was occupied for six months by the Venetians, who performed a numerous amount of extensive work on fortifications although their rule was short. Since, the Castle remained in the hands of the Ottomans until 1922, when Chios was released from Ottoman rule and was annexed to the Greek State.

The Greek State took protection measures in 1924 towards the memorial and with a Presidential Decree in October of 1924 described the Castle as a landmark of archaeological and historic site. However all the above, the memorial was greatly threatened throughout the 20th century, while a portion of the Chian society asked for its urgent demolition, a request which comes up throughout the times, in the 1930s to begin with and then later in the 1950s and the 1970s. Critical for the depreciation and the bad state of conservation of the memorial in the Modern times were physical disasters (earthquakes) of 1881 and 1949, the construction of the new waterfront dock of 1896 that distorted dramatically the Castle’s outer wall close to the port, the mass deployment to the Castle from Greek refugees who fled to Chios after the Asia Minor catastrophe in 1922, the German rule, when bastions and construction materials used for the Castle were used to grind flours. Also, after the Liberation of Chios from the Ottomans in 1912 the walls were stoned, two bastions were partly destroyed and the west gate “ Epano Portello”, along with the parts of the seaside walls with the use of explosives.

The form of the fortification of the Castle of Chios, which every visitor faces is a product of constant retrofits, additions and aids throughout the memorial’s long existence. Throughout times there are strong bastions (eight of which have been preserved today). On three of those bastions there are built plates with Ioustiniani’s emblem (castle with three towers and a crowned eagle), which mention the year of construction or repair of the fortification project in the times of the Genovese rule in Chios (1346-1566). Indicative of interventions that changed the form of the towers and the walls throughout the centuries was the north bastion, which reaches the contribution of the land walls with the seaside, the known bastion of Antonio Zeno or “Zinonos”. The core of the bastion is a tower which was built in late ancient times. In 1426, under Genovese rule, the tower was raised and strengthened, while in 1694, during the short time of Venetian rule, the admiral Antonio Zeno was responsible for the implementation of a new line of additional fortifications at the rampart, which has his name ever since.
The entrance to the Castle is through a bridge which crosses the anhydrous trench, which surrounded the whole perimeter of the city walls. The main gate, Porta Maggiore, preserves its memorial form that the Venetians in 1694. The first building that one meets after the Gate is known as the “Castle of Ioustiniani”, it’s dated to the Genovese rule times and today, restored and running as a place of periodic report of ancient times. In contact with the “Palace” the building of the “Dark Prison” is saved, also a building of the Genovese rule that was associated with a tragic event of the modern history of Chios: here were prisoned in 1822, 70 elders of Chios were driven to the gallows. In the center of the Castle there has been established the cemetery of the eminent Ottomans, who among others is distinguished burial memorial of “Kapoudan Pasa Kara Ali” whose flagship was blown up from Kanaris in 1822, during the period of the Greek Revolution. On the street of Ag. Georgiou, the main road of the settlement, which starts from the center of the Castle and with maneuvers that leads to a seaside wall, preserved are also two muslim mosques: one first comes upon the “Xamidie” mosque, built in 1892 and next the “Eski” mosque, which has been converted to a church of Saint George. On the North-West corner of the seaside wall there has been saved a dilapidated complex of baths (hamam). In the middle of the straight course of the seaside wall and in a small distance from the hamam, the Castle’s medieval tank has been saved and it goes by the name of “Cold Faucet” (Kria Vrisi). The tall horseshoe tower that reaches freely the passageway from all of the sides, called the Koulas, was built during the Genovese rule and it had an unknown cause. Impressive is the use of the ancient construction material that has been walled in its masonry. The “Karnagio”, an elongated building close to “Koula”, is also a building from the Genovese rule, with an unknown original purpose or use. The chapel of Saint Nicholas was built in the modern times in relation with the portside wall in the position of an ancient temple, which has been revealed by an excavation.