The “Historical Sinop Prison” was built in the Inner made of high stone walls which have architectural part belonging to the periods of Byzantium, Roman Empire and Hellenistic. The prison was itself built in 1215, a year after the conquest of Sinop by the Seljuks. As one of the oldest prisons of Turkey, it was established in 1887 within the inner fortress of the centuries-old fortification located on the northwestern part of Cape Sinop. The prison was closed down in 1997 and the inmates were transferred to a modern prison newly built in Sinop.

It is a U-shaped building. In 1839 a building for juveniles was added. A rebellion in 1979 partly destroyed the main building. Famous people who were held here were: Refik Halit Karay, Mustafa Suphi, Ahmet Bedevi Kuran, Refii Cevat, Burhan Felek, Sebahhatin Ali, Kerim Korcan, Zekeriya Sertel The prison facilities were handed over to the Culture and Tourism Ministry in 1999. The fortress prison is currently open to the public for sightseeing purposes.