This is a detail of the Imperial Gate or Babı Hümayün, after entering the palace complex. After Mehmet grounded it is has been changed a lot in later centuries. About a hundred years back a second story that it had for much of its life was taken down by Abdül Aziz. He surrounded the gate with the present marble frame and lined the niches with marble too. Entering the gate we come to the Courtyard of the Janissaries.