The Grand Vizier of the Ottoman Empire ( or Sadr-ı Azam (Sadrazam); Ottoman Turkish: صدر اعظم or وزیر اعظم) was the de facto prime minister of the sultan in the Ottoman Empire, with absolute power of attorney and, in principle, dismissible only by the sultan himself in the classical period, before the Tanzimat reforms, or until the 1908 Revolution. He held the imperial seal and could convene all other viziers to attend to affairs of the state in the Imperial Council; the viziers in conference were called "kubbe viziers" in reference to their meeting place, the Kubbealtı ('under-the-dome') in Topkapı Palace. His offices were located at the Sublime Porte.