The construction of the citadel was commenced by the Bithynians, whereas the Romans, Byzantines and Ottomans made additions or renovations whenever they were deemed neccessary. A significant portion of the cyclopian stones seen as used in the construction of the citadel wall are of Roman origin and are mostly columns, pieces of sarcophagi, statue pedestals, inscribed stone panels. Theses pieces are used densely especially to the east of the citadel gte.
Only the southern section of the citadel walls were reinforced with double-walled five-cornered towers. In the year 1326, the walls of Bursa, recentley captured from the Byzantine Empire, were reinforced with triangular towers by Orhan Gazi. Between the areas of Cakir Aga Hamami and Tophane, there are ruins of three large towers, one of them cylindrical, the other two triangular in shape. Hisar Kapi ( Citadel Door ), located between these two places, was demolished during the earthquake of 1855.
In the walls stretching southwards from Yildiz Kahve ( Star Coffee House ), you can observe round arches and loopholes. The Kaplica Kapi ( Spa Gate ) is located in front of the coffee house. Then the walls mostly in ruins continue towards the Zindan Kapi ( Dungeon Gate ). The angled tower next to the Zindan Kapi was built Celebi Sultan Mehmet in the year 1418.
This section of the walls is realtively well-preserved, and continues from Zindan Kapi to Uftade, and then on to join the Pinarbasi Kapisi ( Spring Gate ) and back to the Cakir Aga Hamami. The walls that extend parallel to each other between the Pinarbasi an Zindan gates have been stripped of their cut stone sections, whereas only the sections made of unhewn stone and lime and sand mortar remain upright today. The second row of walls between Pinarbasi Gate an Zindan Gate are now lost between houses. The remaining wall section in this neighborhood was sverely damaged in order to construct houses and partitions.
Today Bursa citadels restorating by Goverment of Bursa.