Heptapyrgion (Thessaloniki)

The Heptapyrgion (Ancient Greek: Ἑπταπύργιον), modern Eptapyrgio (Επταπύργιο), also popularly known by its Ottoman Turkish name Yedi Kule (Γεντί Κουλέ), is a Byzantine and Ottoman-era fortress situated on the north-eastern corner of the acropolis of Thessaloniki in Greece. Despite its name, which in both languages means "Fortress of Seven Towers", it features ten, and was probably named after the Yedikule Fortress in Constantinople (modern Istanbul, Turkey). It served as the major redoubt of the city's acropolis, as well as the seat of its garrison commander in Ottoman times, until the late 19th century. It was then converted to a prison (Φυλακές Επταπυργίου), which remained open until 1989. References to the infamous Yedi Kule prison abound in the Greek rebetika songs. Restoration and archaeological work began in the 1970s and continues to this day.

The Heptapyrgion is located in the north-eastern corner of the city's acropolis. Although the urban core of the city essentially dates from its foundation by Cassander in 316 BC, the walls that defined the medieval and early modern city, and that are still visible today, date to the late Antiquity, when the Roman emperor Theodosius I (r. 379–395) fortified the city anew. The five northern towers of the Heptapyrgion, along with the curtain wall that connects them, forming the northern corner of the acropolis, probably date to this period. Another theory, dating their construction to the 9th century, has also been brought forth.

The southern five towers and wall were built likely in the 12th century, thus forming a fortified redoubt in the interior of the city's citadel. This fortress was then maintained and rebuilt in the Palaiologan period. The nature of the reconstruction and dating of the southern portion of the fort is disputed. There is no reference to this fort in the older literary sources, and the later ones are often ambiguous: a kastellion ("fortress") is mentioned in 1208–1209, a castellan with the Tzakones of the castle" in 1235. At the same time, the koulas (from Turkish: kule, "fort") of Thessaloniki, present in the chronicles of the 14th and 15th centuries, could refer to the entire citadel, and not just the Heptapyrgion.

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