The main exterior gate of the Topkapı Palace is the Imperial Gate (Bab-ı Hümayun) which opens up to the Ayasofya Square. This gate leads to a garden known as the First Court. This court has the Aya Irini Church which was once used as an ammunition depot and behind the Church there is the mint. In the past various pavillions allocated to different services of the palace were located in the First Court. In later years these have ben replaced with public buildings and schools. Some of these are still existing. At the end of the 19th century Archeology Museum and School of Fine Arts (now Oriental Works Museum) were built in the large garden which is to the northwest of the First Court. The oldest structure in this section is the Çinili Köşk built by Fatih, which is now used as the Museum of Turkish Tiles and Ceramics. On the walls of this outer garden facing Bab-ı ali (the Imperial Gate), there is Alay Köşkü (procession Pavillion) where the Sultans used to watch the marching ceremonies. A section of the outer garden was planned by the municipality at the beginning of the 20th century and opened to the public. Known today as the Gülhane Park, the entrance has one of the larger gates of the palace.  After the First Court, there is the Second Court which contains the palace buildings. It is entered through a monumental gate called Bab'us-Selam or the Middle Gate. The buildings in this court form the outer section of the palace which is called Birun. On the right there are the instantly noticed palace kitchens with their domes and chimneys and the dormitories of those who worked there. The most important of the buildings on the left side of the court are the Kubbealtı and the Inner Treasury. Behind Kubbealtı rises the Justice Tower, which is one of the symbols of the Topkapı Palace. The Harem section, which comes all the way to the back of these buildings is entered from the Third Court. Third Court is entered through the gate called Bab'üs Sa'ade (Gate of the White Eunuiches). This section of the palace is called Enderun, and it is the section where the sultans live with their extended families. Hence it is specially protected. The barracks of the Akağalar, which guard Bab'üs Sa'ade are on both sides of the gate. There are two structures. The first which is immediately opposite the gate is the Throne Room or the Audience Hall. Here the sultans receive the ambassadors and high ranking state officials such as Grand Visier or the Visiers. Right behind the Throne Room there is the library built by Ahmet III (1703 - 30). On the right side of the Third Court, there is the barracks of the Enderun and the Privy Treasury which is also known as the Mehmet the Conqueror Pavilion. On the side facing the Fourth Court, there is the Larder Barracks of the Enderun, the Treasury Chamber and the Chamber of the Sacred Relics. The left side starts with the Harem. The harem which covers a large part of the Palace consists of about 60 spaces of varying sizes. The main structures which are located in front of the Harem, facing the Third Court are Akağalar Mosque, Sultan Ahmet Mosque, Barracks of the Sacred Relics Guards and Chambers of the Sacred Relics. Here, the sacred relics brought back by Sultan Yavuz Selim from Egypt in 1517 are kept. The Fourth Court is entered from a covered path going from both sides of the Treasury Room. Here the buildings are located in the first part of the court, which has two sections of different levels. On the left side of this section called Lala Garden or Lale Garden there is Mabeyn which is the beginning point of Harem's access to the garden, terrace for the ladies with removable glass enclosure, Circumcission Room, Sultan İbrahim Patio and another one of the symbols of Topkapı palace, the İftariye (or Kameriye) and Baghdat Pavilion. This pavillion was built by Murad IV in 1640 to commemorate the Baghdat Campaign. At the center of the first section of the Fourth Court, there is the Big Pool and Ravan Pavillion next to it. This pavillion was also built by Murad IV in 1629, to commemorate the Revan Campaign. The side facing the second section has Sofa Pavilion (Koca Mustafa Pasha Pavilion), Başbala Tower and Hekimbaşı (Chief Physician) Room. The Sofa Mosque and Esvap Chamber and the latest built Mecidye Pavilion are on the right hand side of the Fourth Court. Out of the pavillions built on the shore of the Marmara Sea, only Sepetciler Mansion has survived until the present.