The Kayseri Castle, which mainly comprises a central Citadel and outer walls, has been the most prominent element of the city square. An architectural competition was held for the Citadel in 2008, and the implementation of the winning project that aimed to refunction the Citadel was completed in 2019. This project is arguable in terms of how the museum concept is handled. Rather than considering the area as an open-air museum with its history, architectural background, possible excavation results, and current position in the city center, the implemented project seems to prefer to organize the Citadel as an open public space. This has turned the archaeological site into an anonymous and unused area completely disconnected from its historical context. This study aims to argue the necessity of museology to create a successful example of adaptive reuse. The study first summarizes the historical and archaeological qualities of the Citadel. Then, the information on the change of the Citadel in the twentieth century and the latest project is given. A field study is realized to determine the public usage of the area. Conclusively, recommendations for the Kayseri Citadel are made on the museology policies regarding the adaptive reuse principles.