During Seljuk Sultan Sanjar’s reign the Shahriar Ark was constructed - a citadel within the citadel, protected by its own walls and moat. It housed crucial governmental and military buildings.

One of those construction is what is today called “kepterkhana”, an interesting corrugated structure, which is the best-preserved within the citadel. It’s walls still survive to a height of some 4,5 m, but its function remains debatable: from library to pigeon house.