The name has its origins in the old Oriental practice in which the ruler announced his official decisions and judgements at the gate of his palace. This was the practice in the Byzantine Empire and it was also adopted by Ottoman Turk sultans since Orhan I, and therefore the palace of the sultan, or the gate leading to it, became known as the "High Gate". This name referred first to a palace in Bursa, Turkey. After the Ottomans had conquered Constantinople, now Istanbul, the gate now known as the Imperial Gate (Turkish: Bâb-ı Hümâyûn, leading to the outermost courtyard of the Topkapı Palace, first became known as the "High Gate", or the "Sublime Porte".
When Sultan Suleiman the Magnificent sealed an alliance with King Francis I of France in 1536, the French diplomats walked through the monumental gate then known as Bab-ı Ali (now Bâb-ı Hümâyûn) in order to reach the Vizierate of Constantinople, seat of the Sultan's government. French being the language of diplomacy, the French translation Sublime Porte (the adjective being unusually placed ahead of the word to emphasise its importance) was soon adopted in most other European languages, including English, to refer not only to the actual gate but as a metaphor for the Ottoman Empire.
In the 18th century, a new great Italian-styled office building was built just west of Topkapi Palace area, on the other side of Alemdar Caddesi street. This became the location of the Grand Vizier and many ministries. Thereafter, this building, and the monumental gate leading to its courtyards, became known as the Sublime Porte (Bab-ı Ali); colloquially it was also known as the Gate of the Page (paşa kapusu). The building was badly damaged by fire in 1911. Today, the buildings house the provincial Governor of Istanbul.