Located in the interior of the Ismaili Qasba, this historic monument dates from the early 18th century, well renowed as a vast dark underground built as a maze. Known as Habs Qara, this name comes from the surname of a Portuguese prisoner who received from the Alawite Sultan Moulay Ismail the promise of release if he managed to build a prison of more than 40,000 prisoners. This prison consists of three rooms composed of a series of arcades resting on pillars of an average size of 1.40 m by 3.46 m and supporting vaults in lowered drums. A staircase leads to Koubet Al Khayatine. After the reign of the sultan, this prison was used temporarily as silos and food stores.