This paper explores how urban landscapes of Islam in Istanbul were transformed into new objects of heritage in 1950s Turkey. This was a key period in Turkey’s history. Following the end of one-party rule in 1946, some of the restrictions on public religious worship in Turkey were dismantled or reconfigured. For examples, the language of the call to prayer was switched from its Turkish translation back to Arabic; religious schools (imam hatip liseleri) were opened across the country; and newspaper and magazine articles about Islam became a part of an expanded public culture. While scholars have helped to document the dynamics of these changes, they have had less to say about the projects of conservation, restoration, and development that reshaped many of Istanbul’s Ottoman-era mosques, tombs, and medreses during this period. Yet although these urban landscapes of Islam signaled a new public visibility of religion, these projects of conservation, restoration, and development also transformed what these buildings meant. They came to occupy an ambivalent position as both sites of religious practice and sites of heritage. This paper focuses on the work of the architect and architectural historian Ali Saim Ülgen, who played a key institutional and intellectual role in carrying out many of Istanbul’s conservation projects in the 1950s. Situating Ülgen’s work within the broader cultural and urban context of 1950s Turkey, this paper expands our knowledge of the ways that Islam came to be practiced and understood in public during a crucial moment of transformation.