Heptapyrgion, also known as “Yedi Kule”, on the North-East far end of the Acropolis, is one of the Balkans’ most emblematic fortification complexes, which was reinforced and implemented since paleochristian-early byzantine era, up to the years of Ottoman occupation. Due to its seven (hepta) towers, in its initial form, it was given the name “Heptapyrgion”. In the 19th century it operated as a prison, with new buildings being added to the complex to improve its functionality. This prison was shut down in 1989 and was given to the Greek Ministry of Culture.