Both Genoa and Venice profited by the frequent dynastic quarrels among the members of the Byzantine imperial family to increase their influence and obtain trade rights. They also secured for their merchants a sort of capitulation rights, by which the merchants could form colonies, under the direct jurisdiction of their consular representatives. Galata therefore evolved into a type of independent city-state, similar to those existing in Italy. Because the Genoese central government was rather weak, Galata rulers often took sides in the continuous fights among Byzantines, Serbs, Ottomans, Bulgarians, which responded to their immediate advantage, rather than to the policies of their distant motherland. They strengthened the defenses of Galata by building a very high tower on the top of the hill (it is clearly visible in the map above).
In 1453 Sultan Mehmet II Fatih (the Victorious) laid siege to Constantinople. While a Genoese leader of soldiers of fortune, Giovanni Giustiniani Longo, responded to the appeals for help of the Byzantine Emperor Constantine XI, and with his 700 soldiers was able to effectively organize the defense of the city, the Genoese of Galata proclaimed their neutrality and as a matter of fact helped the Ottomans, by leaking information and by allowing them to move their fleet by land from the Bosphorus to the Golden Horn through a sort of railway built on the hill of Galata next to the walls of the town. As a result of this policy, Mehmet II, after having conquered Constantinople, renewed to the Genoese of Galata their trading rights. He required however the tower to be lowered and the walls to be broken in several places.
The reason why the Genoese built such a high tower can be easily understood, by going up to its terrace. The tower allowed the view of the open sea beyond the hills and the buildings of Constantinople, so that the Genoese could early detect the arrival of their own ships or of hostile fleets.