Sustainable design movement in Turkey and across the world mostly focuses on new buildings, with little attention on existing built heritage. Nonetheless, historical building heritage constitutes a majority of the built environment in Turkey. According to the statistics of Turkish Ministry of Culture and Tourism, there were 106.359 registered immovable cultural heritage in all around Turkey at the end of the year 2017. It is thus important to investigate sustainable development potentials and make suggestions for conserved built heritage. The aim of this research stems from the importance of finding a clear visualization for urban design for cities in the present and future by means of sustainable development, which satisfies the needs of the present and protects the rights of the future. Hence, this manuscript first examines the sustainability potentials of a case study in the 16th century Kursunlu Mosque with its neighbourhood, located in the historic Ulus district in Ankara, Turkey. This research investigates the importance of studying the term 'urban conservation' within the context of historic Ulus area. Although the mosque is nearly walking distance to historic touristic destinations of Ankara such as the Castle, Ahi Elvan and Ahi Serafettin Mosques, Cengel Khan (Museum), Cukur Khan, Safran Khan and Hamamonu area, it does not attract much of the visitors, because of its lack of integrity with the nearby built environment and its restoration necessity. Research methods include literature and archival survey, in-situ observations, and interview with the local community. The analysis reveals urban conservation potentials of the area and sustainable development suggestions for the mosque with its neighbourhood. The major conclusion of the research is that sustainable development suggestions as well as conservation measures of the case study mosque and urban conservation analysis may provide the user and visitor increase and contribute to the revitalization of the building and the neighbourhood area in the long term.