In the study of the formation of early Islamic art and architecture, the presence and role of late antique Christian religious buildings are elements still largely overlooked. Recent discoveries, mostly due to epigraphic and archaeological studies, have revealed the existence of churches and the foundation of new ones falling chronologically far beyond the traditional boundary of the Islamic conquest. 1 While for various reasons this phenomenon has become particularly evident in rural areas, the analysis of churches located in towns at the time of the Islamic conquest still presents a sort of paradox: while it is well known that the majority of the population was Christian at least until the tenth century, 2 its architecture, art, and material culture, starting with places of worship, appear neither in the common narrative of early Islamic history and art nor in histories of the Christian communities in the Dār al-Islām. 3 With the exception of the Church of the Holy Sepulchre and its interrelation with the Dome of the Rock, almost none of the churches used by the Christian communities in the cities of Bilad al-Sham are mentioned in discussions of the formation of early Islamic art and architecture. Starting with the city of Urfa (known as Edessa and al-Ruha in ancient times), this article examines the presence and role of late antique churches in the urban context of the medieval Dār al-Islām. In particular, we will attempt to clarify the connection between these churches and the mosques in the cities under investigation. Such a relationship moves from one of simple coexistence to substitution, the latter due to the neglect of late antique churches caused mainly by the diminishing Christian presence and the changing attitudes of Muslim societies towards their religious minorities. Within this framework, the way in which Muslim patrons searched for and reused late antique/Byzantine artifacts for their new mosques represents a faithful mirror of the shifting status of churches over the centuries. Because of the history and structure of the academic fields involved in this analysis, some periods in Urfa’s past have received more attention than others. The recurring reference to Urfa in early twentieth–century academic literature, for instance, was motivated by the significant role the city played in the early stages of Christianity. 4 More recently, because of a new approach to studying early Islamic history, several scholars have successfully worked on a remarkable number of literary sources produced within the local (northern Syria and northwestern Mesopotamia) Christian communities, seeking to further explain the critical period of the seventh century by examining some of the non-Muslim accounts of the Islamic conquest. 5 Finally, the early modern and modern eras of the city have been the subject of intense discussion since the documents of the Turkish archives began to shed new light on the life of this provincial city during the Ottoman period. 6 The medieval period (seventh to fifteenth centuries) 7 has often been considered an extension of the late antique/Byzantine period, following a pattern of decline culminating in the Crusaders’ defeat. 8 In addition, because of the absence of monumental remains and archaeological excavations, the reconstruction of Urfa’s pre-Ottoman urban fabric and buildings has been particularly difficult. 9 Hence, the religious art and architecture of the medieval period still lack further interpretation since they appear somehow hemmed in between the memories of the late antique/Byzantine past and the Ottoman monuments still visible in the city today. In exploring medieval Islamic Urfa, this essay will integrate Christian art and architecture into the discussion …