The imposing hisar (citadel) is the most interesting part of Ankara to poke about in. This well-preserved quarter of thick walls and winding streets took its present shape in the 9th century AD, when the Byzantine emperor Michael II constructed the outer ramparts. The inner walls date from the 7th century.
Parmak Kapısı is the main gate. From here, meander the main alleyway to Alaettin Cami, the citadel mosque that dates from the 12th century. It has been extensively rebuilt over the years and in 2019 was again undergoing a thorough restoration that is planned to be finished by mid-2020. To your right a steep flight of stairs leads to the Şark Kulesi, with panoramic city views. If you look to the north from here you'll see the Ak Kale (White Fort). It is out of bounds to visitors, though there are more good views from near its hilltop perch if you follow the alleyway leading up to the tower.
Some local families still live inside the citadel walls and the houses often incorporate broken column drums, bits of marble statuary and inscribed lintels into their walls. For a long time the neighbourhood here was extremely run-down but the past few years have seen the area gentrified somewhat, although once you duck off the main route there are still many narrow, ramshackle alleys to explore.