Ben Youssef Mosque
The Ben Youssef Mosque (also known by its English spelling as the "Ibn Yusuf Mosque"), is a mosque in the medina quarter of Marrakesh, Morocco, named after the Almoravid emir Ali ibn Yusuf. It is arguably the oldest and most important mosque in Marrakesh.
The first mosque in Marrakesh was erected by the Almoravid emir Yusuf ibn Tashfin in the 1070s, to serve as the central congregational mosque of the fledgling city. It was one of the first brick buildings in the city, and Ibn Tashfin is said to have been personally engaged in mixing the mortar and laying of the bricks.  His son and successor Ali ibn Yusuf ("Ben Youssef") built a grand new central mosque, named the Masjid al-Siqaya ("mosque of the fountain") on account of the large fountain with a marble basin in its courtyard. It cost nearly 60,000 gold dinars, and was completed sometime between 1121 and 1132. It was the largest mosque built in the Almoravid empire, with a rectangular base of 120 by 80 meters, and a minaret estimated to be thirty meters high. The rising city's layout was organized around it, and together with the neighboring souqs, it formed the center of early Marrakesh's city life. The nearby Koubba Ba'adiyn was one of the monumental ablution fountains connected to it.
When the Almohads defeated the Almoravids and captured Marrakesh in April, 1147, the original mosque was deemed by the Almohad caliph Abd al-Mu'min to have an orientation error (its mihrab was pointing some six degrees south of Mecca) and was promptly demolished. The Almohads erected a new reoriented central mosque on top of it. However, the Almohads were unable to eliminate its popular appellation, and it continued to be commonly known as "Ali ibn Yusuf's mosque" ("Ben Youssef" in French spelling).
The Ben Youssef Mosque was refurbished around 1563, on the orders of the Saadian sharif Abdallah al-Ghalib. It was around this same time that the city's layout began to be changed, with new residential areas and souqs located further west, by the Koutoubia Mosque and the new al-Muwassin Mosque, shifting the center of gravity away from the old Ben Youssef mosque. Over the cleared space, the Saadians erected a great new theological college (madrasa), the Ben Youssef Madrasa in 1563-64, just east of the mosque, thereby giving it a new life as the mosque of scholars. 
Having fall into ruin in the course of the 17th and 18th Centuries, it was almost completely rebuilt in early 19th Century by the Alaouite sultan Suleiman, with hardly any trace left of its original Amoravid or Almohad design. 
It continues to serve today as one of the most important mosques in Marrakesh. Traditionally, the qadi (religious judge) of the Ben Youssef Mosque has jurisdiction over all of Marrakesh, and even over outlying areas. It is not accessible to non-Muslim visitors.
- Messier (2010: p.55-56)
- Cenival (2007: p.331)
- Messier (2010: p.123,p.214-15)
- Messier (2010: p.168)
- Lamzah (2008:p.60)
- Lamzah (2008: p.60); Bloom and Blair (2009: p.466)
- Van Hulle (1994: p.43)
- Cenival (2007: p.321)
- Bloom, J.M. and S.S. Blair editors, 2009, The Grove Encyclopedia of Islamic Art & Architecture. Oxford: Oxford University Press. pp.465-66
- Cenival Pierre de (2007) "Marrakesh", new edition of 1913-36 article, in C.E. Bosworth, editor,Historic Cities of the Islamic World, Leiden: Brill p.319-32 preview
- Julien, Charles-André. (1931) Histoire de l'Afrique du Nord, vol. 2 - De la conquête arabe à 1830, 1961 edition, Paris: Payot
- Lamzah, Assia (2008) "The Impact of the French Protectorate on Cultural Heritage Management in Morocco: The Case of Marrakesh", Ph.D dissertation, Urbana: University of Illinois. online
- Messier, Ronald A. (2010) The Almoravids and the Meanings of Jihad. Santa Barbara, Calif.: Praeger.
- Van Hulle, Jean-Claude (1994) Bienvenue à Marrakech. Paris: ACR.