The Prison de Kara is a network of underground vaults beneath the Imperial City, once used to imprison European captives and criminals. Moulay Ismail held tens of thousands of captives — Spanish, Portuguese, and other Europeans — whom he used as slave labour to build his imperial capital. The conditions were brutal, and the vaults where they were confined still have a sinister atmosphere.
The prison is accessible through the Heri es-Swani complex. The entry fee is small, and a guide is useful for navigating the underground passages. The scale of the captivity operation here — and its role in constructing one of the great architectural achievements of the Islamic world — is a complex and uncomfortable story well worth understanding.