Its name is due to its vicinity of the Ben Youssef Mosque but actually it was built by the Saadien Moulay-Abdellah around 1564. It is of mérinide inspiration and resembles the médersas of Fés . It was the largest medersa of the Maghreb but its proportions remain balanced. One is surprised by the silence which reigns there whereas one is in the middle of the Médina . In the entrance hall, a tank for ablutions is curiously decorated with floral and animal motives, it would come from Curdour .