Ankara Castle (Turkish: Ankara Kalesi) is a fortification from the late antique/early medieval era in Ankara. The castle is composed of an inner line of walls with closely spaced towers that encloses an area of about 350m by 150m, and an outer line of walls with towers some 40m apart. Both sets of walls were constructed using large quantities of reused masonry. The exact date of their construction is uncertain, but both postdate the capture and destruction of Ankara by the Persians in probably 622. Foss considers that the inner walls may date from the reign of Constans II. The outer walls are generally believed to have been constructed slightly later.

Source: https://en.wikipedia.org/wiki/Ankara_Castle