This is the Pipe Room of the quarters of the Zülüflu Guards. Or, (wonderfully!) in English, Axe Wielders-with-Tresses.
The green panels on the right are the doors to lockers for storing their pipes. The room's ceiling was quite high, with windows at the top so the Axe Wielders-with-Tresses did not become the Asphixiated Axe Wielders-with-Tresses.
Originally the Guards cleared the way for the army using axes. By the time they ended up in the palace, they had become palace functionaries. They cleaned the palace Harem, took care of the sultan's messages, moved heavy stuff -- like thrones and coffins -- around, carried firewood, did set up and take down for ceremonies, and guarded the sultan's imprisoned relatives.
Some of them had impressive titles like Supplier of the Pantry, Producer of Dried Fruits and Nuts, Water Pipeline Builder, and Runner.
Supposedly the braids hanging down on either side of their conical headgear and their turned up collars hindered them from observing the surroundings in the Harem.