It is unclear exactly when the Genoese began to build the walls of Galata. By 1308, the Genoese were purchasing land beyond the borders granted by the emperor and began to build a series of fortified houses that were converted into defensive towers with windows modified into arrow slits. Much of the quarter including the Palazzo Comunale burned down in 1315 and was rebuilt in 1316. During this time, it seems that proper fortified walls were also built, despite the prohibitions of previous agreements. During a secondary phase of construction, a small rectangular castle was built on the western flank of the Palazzo Comunale by 1335, during which time other fortifications were being built north of the quarter determined by previous agreements. It also seems that the heights of the walls were increased during this phase of construction. Following their occupation of Mytilene in 1333, the Genoese began to illegally expanded their quarter at Pera. In 1336, when Andronikos III recaptured Lesbos from the Genoese, the emperor ordered these walls to be demolished, though it is unclear how well was this implemented. While they were given permission to purchase adjacent vineyards, the Genoese continued to expand and fortify their quarters far beyond this area, towards the hill where they would build Galata Tower (known as Christea Turris or “Tower of Christ”) in 1348. The area around Galata Tower was probably enclosed with walls the following year.

This secondary phase of the construction of fortifications also corresponds to the civil war between John V Palaiologos and John VI Kantakouzenos in 1341-1347 and the war between in the Genoese and Byzantines over customs duties in 1348-1349, during which the imperial fleet was destroyed and a major fire broke out in Galata. It also corresponds with the outbreak of bubonic plague in Europe, which seems to have been first brought to Constantinople in 1347 by Genoese ships traveling from Crimea, after which it then spread across Europe. In 1351, the Byzantines unsuccessfully attempted to capture Galata. The next major construction phase of Galata’s walls took place after the Byzantine fleet was defeated by the Genoese in 1352, which concluded with a treaty officially extending the Genoese quarters of Galata to the east. This, in turn, was followed by another Byzantine civil war in 1352-1357. This period involved a significant decline in Byzantine fortunes, while at the same time Galata increasingly flourished and acted more independently.

It is uncertain when the Fort of Galata was actually it was handed over to the Genoese, though it was certainly by the year 1384. By the time it became a possession of the Genoese, it was known as the Castle of Holy Cross (Castrum Sancte Crucis). Around this time, a tower (known as the Tower of the Holy Cross) was added to the structure, over which a gilded cross was placed in 1391. A bell was added to the castle in 1390, which perhaps was used to give warning signals. Eventually, the fort was linked to the walls of Galata, during which time it might have also functioned as an arsenal. It is generally held that the Genoese acquired the northwestern district in 1387, the western district Spiga in 1397, and the eastern district Lagirio around 1400, though there is evidence suggesting that the Genoese controlled Spiga by 1351 and Lagirio in 1376. Repairs made to the wall in 1390-1391 were likely made in expectation of an Ottoman attack, though the blockade of Bayezid I halted defensive constructions until 1435. An unsuccessful Ottoman siege of Galata took place in the late 14th century and again in 1411 and 1422. The Milanese occupation of Genoa in 1421-1435 likely slowed additional defensive construction. In 1427, Benedictine monks founded the Church of San Benedetto (now St. Benoit) in the district of Lagirio. The last known pre-Ottoman slab records work in 1452 supported by Pope Nicholas V, who was of Genoese origin.  

Galata surrendered to the Ottomans in 1453 following the conquest of Constantinople. While Mehmet II promised that the fortifications of Galata would be spared, several sources mention that he ordered the walls to be demolished. However, there is little evidence that any significant Ottoman reconstruction took place and the walls were largely extent until the late 19th century. Perhaps the textual references to the destruction of the walls only refer to a symbolic destruction of the upper sections of the walls that would  have limited their defensive function. The earthquake of 1509 caused  upper sections of Galata Tower to collapse. Galata would suffer from a sequence of fires and earthquakes over the next few centuries, though the damage it caused to Galata’s walls was not recorded. The local municipality began to demolish the walls in 1864, though the walls were well-documented before this began. Today only a few sections of the walls and its towers survive – though much more of the walls survive than is commonly known. Several sections of walls and one gate still exist. In addition, there are two slabs in situ and several other slabs from the Walls of Galata are now at Istanbul Archaeological Museums.

Also see Galata Tower and Galata Slabs