The Ottomans enforced some policies to restructure the new cities and communities they have been ruled, especially in Southeast Europe. They tried to form a mental image with Islamic features to eliminate the long-standing original image of these cities; this process is historically known as the Ottomanization of European city which was a natural result of urban and architectural activities. The present study addresses the general policies and the methods of the Ottomans when dealing with Christians in European cities and legalizing their situations to suit the new ruling system since the mid-15th century. Accordingly, various social, architectural, and urban changes took place within the new community framework. The study investigates the mechanisms of the Ottomanization of these European cities in general and specially the old city of Rhodes from 1523 to 1912 AD, including having an integrated urban policy that resulted in a considerable development of the existing urban communities or establishing new ones on the outskirts of towns. They relied on Turkish immigration to create communities containing the Turks and the local inhabitants. Therefore, they employed endowments whose works were the basis of the development of new urban communities. Thus, the Ottomans have been changed the population demography and adding the symbolic Islamic elements to the old buildings such as the minarets, minber, mihrabs and Arabic inscriptions. The field study surveyed the architectural elements and buildings in the old city of Rhodes and how they were reused and converted into mosques. The change of function was followed by a change of the form through the additions that reflect the ideology and thinking of the new ruler. The main question of the paper is; how the Ottomans had been changed the symbols of Christian cultural heritage of the town of Rhodes to Ottoman or Islamic one?. Also, if them policies were the same in all European cities or not?.  It could be said; that Ottomanization was one of the important issues that preoccupied the Ottoman rulers since the early Ottoman Empire possible because the Sultans thought that such efforts represented the soft power to create and install a mental image among the indigenous population that the Ottomans sought the settlement and development of Ottoman Islamic societies