Kara Prison

Qara Prison or Habs Qara (Moroccan, also Moroccan, lit. 'Prison of the Christians'), also known as the Prison of the Christian Slaves, is a series of underground vaulted chambers built in the early 18th century in Meknes, Morocco, by order of Sultan Moulay Ismail. Although popularly described as an underground prison that could host thousands of inmates, mostly Europeans captured at sea, most scholars agree that its function was to serve as a vast storage space for the royal complex of the Kasbah of Moulay Ismail.

Prison data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).