The initial fortification of the city of Chania, surrounding the hill of Kasteli, is founded over the remains of an older fortification of the Hellenistic period. The larger part of the Byzantine wall was constructed by the ruins of ancient Kydonia, which were used as building material. Its outline is irregular and consists of rectilinear parts interrupted by small oblong or polygonal towers. In some parts, the wall simply complements the natural fort created by the rock. The wall has four gates, from which none preserved its initial formation to our days.  The two main gates were the west gate to the plateau "Santrivani" and the east gate on the crossroad of the streets "Kanevaro" and "Daskalogianni". The other two smaller gates were located on the southern part (on the meeting point of the streets "Katre" and "Karaoli-Dimitriou") and on the northern part near the Turkish prisons (today the secretariat of the Polytechnic School of Crete) that led to the street "Afentoulief".