Sultan Hassan is a unique building in Cairo, as its function was not praying only but it was also a school for the four Sunni schools of thoughts : Shafi'i, Maliki, Hanafi and Hanbali, so it was a full complex (Mosque and School).
The structure has been built in the time of Sultan Hassan bin Mohammad bin Qala'oun in the Memluk period. The work for completing the complex was continues for three years with no idleness but it has never been finished in the rule of Sultan Hassan, but in his successor’s reign after full seven years to complete the whole structure.
Sultan Hassan ruled Egypt twice, as In the first time he was 13 years old and that was in 1347 AD, and then he was dethroned by his princes and high officials, but he ascended the throne again in 1356 but before controlling the country and expelling them, other generals managed to kill him because he was not powerful and he never actually controlled the country. The story of his murder remained obscure and also his body did not appear.
The mosque was built near to the Citadel of Salah El-Din, it is the largest mosque in the Islamic world, there is a theory saying that the cost was exaggerated as it was 20.000 Dirham per day, which is quite a lot, the mosque was meant to have four minarets, but three only has been built, and while completing building one of them has collapsed causing the kill of more than three hundred people and it has now only 2 minarets for the time being.
This complex was a mosque and schools as mentioned before, and it is so clear in the inner design of it, it consists of a main court for praying called sahn surrounded from its four sides with the four schools.
The façades of the Mosque are one of the main features of the Mosque because of their large size. In the Northern façade you will find the main entrance of the mosque, which leads to a lobby covered with a dome, this lobby will lead you to the sahn which includes a very large fountain in the middle for the ablution, and at the four corners there is a small door in each side leads to one of the four schools for teaching the four doctrines. Each school consists of Iwan, Sahn with a fountain, three floors overlooking the sahn, those floors were used as the houses of the teachers and the students. The eastern Iwan is the largest one, because It is The Qibla Iwan, it includes some beautiful elements like, The Mihrab, The Minabr which has been made out of White Marbel, Dekkat –Al-Muballegh (bench for calling for the praying time) made also out of marble. Finally the whole inner walls of the eastern iwan were covered with colored marble.
The last unique feature of the mosque is the Mausoleum, the mausoleum is inscribed with reliefs to determine the date of completing the structure which was 764 A.H. This Mausoleum includes a cenotaph which was supposed to be the tomb of Sultan Hassan, but he has never been buried there, as his body never appeared, instead his sons were buried there.