Cairo’s House of Knowledge

Although the building that held Cairo’s Dar al-’Ilm, or House of Knowledge, disappeared long ago, it stood not far from the Mosque of al-Aqmar, right, along Muizz Street, a thoroughfare that dates back to the founding of Cairo in the 10th century.
"On March 24, 1005, a man reputed for madness came to his senses long enough to establish one of the most progressive and influential academic institutions of the Middle Ages. 'On this Saturday ... the so-called House of Knowledge in Cairo was inaugurated,' wrote the chronicler al-Musabbihi, a friend of the new institution’s founder, Caliph al-Hakim, who had assumed his title nine years before. Though al-Musabbihi’s original manuscript is lost, copied sections survive in the writings of 14th-century Egyptian historian al-Maqrizi. As al-Musabbihi and others at court well knew, staying on al-Hakim’s good side could be tricky. The 'Mad Caliph,' as he was later called, could be mingling jovially with his subjects in the streets at one moment and ordering the summary execution of an esteemed courtier the next—or the extermination of the city’s dogs because their barking annoyed him. ..."
AramcoWorld

Dar al-’Ilm drew scholars from across the Muslim world. It was established in 1005 with books donated by Caliph al-Hakim, whose own palace library was said to hold some 400,000 volumes.