In fourteenth-century Bithynia--what is, today, northwest Turkey-- power changed hands from the Byzantines to the Ottomans. In turn many scholars have viewed the Byzantine and Ottoman cultures as separate and, consequently, their architecture as belonging to distinct traditions. This paper suggests, instead, that a study of the built environment in Bithynia helps eliminate, or at least blur, the divisions imposed by political history. To begin with, the similarities between the Byzantine and Ottoman regional styles in architecture are so striking that they cry out to be studied together. Although the region was the center of the Byzantine government during the thirteenth century, by the third decade of the fourteenth century, its major centers had fallen to the Ottoman Turks, who established their capital at Bursa (Byzantine Prousa) in 1326. From a Byzantine perspective, the Late Byzantine architecture in Bithynia represents the end of regional tradition, while from the Ottoman viewpoint, the early Ottoman buildings appear incongruous to the canons of Classical Ottoman architecture. To consider buildings as cultural artifacts presents an alternative way of looking at the complexities of the period and moving beyond the limited textual record. The historian Colin Imber has called the fourteenth century a "black hole" in the formation of the Ottoman state because of the paucity of textual evidence on both sides, both the Byzantine and the Ottoman. Indeed, none of the recent studies of the early Ottoman state looks beyond the written evidence in constructing a history. In Bithynia architecture can provide what the texts cannot; with its many late Byzantine and early Ottoman buildings, the region embodied the complexities of the period, since its very urban landscape served as an agent of identity mixing and cultural exchange across the frontier line. Many Ottoman buildings in the region borrow from Byzantine construction techniques, sometimes simply for aesthetic reasons, sometimes to make a political statement emphasizing Ottoman hegemony, and in all cases suggesting an overlay between the Byzantines and Ottomans. Buildings thus function as a synecdoche for the heterogeneous cultural allegiance of their builders, while sustaining a public profile that all members of the society, Muslim, Christian, and Jewish alike, can appreciate from their own perspective.