The main gate is called the Imperial Gate (Arabi: Bâb-ı Hümâyûn or Greek: Porta Augusta), also known as Gate of the Sultan (Turkish: Saltanat Kapısı) located to the south [2]. This massive gate, originally dating from 1478, is now covered in 19th-century marble. The massiveness of this stone gate accentuates its defensive character. Its central arch leads to a high-domed passage. Gilded Ottoman calligraphy adorns the structure at the top, with verses from the Holy Koran and tughras of the sultans. Identified tughras are of Sultan Mehmed II and Abdül Aziz I, who renovated the gate. On each side of the hall are rooms for the guard. The gate was open from morning prayer until the last evening prayer. No one apart from viziers and foreign dignitaries was allowed passage through the gate. According to old documents, there was a wooden apartment above the gate area until the second half of the 19th century. It was used first as a pavilion by Mehmed, later as a depository for the properties of those who died inside the palace without heirs and eventually as the receiving department of the treasury. It was also used as a vantage point for the ladies of the harem on special occasions.
The Imperial Gate is the main entrance into the First Courtyard.
