The Koubbat as-Sufara’ was once the reception hall for foreign ambassadors and it's here that Unesco chose to place its World Heritage inscription when the city was designated in 1996. In front of the building is a broad clearing pockmarked with small subterranean windows providing light for a vast 40-hectare crypt of similar construction to the granary at Heri es-Souani. Take the stairs down to the right of the entrance to Koubbat as-Sufara’; the entrance fee covers both.

The dark and slightly spooky network of rooms below ground was a mystery when discovered. Historians now believe it was used for food storage, although tour guides will delight in recounting the (erroneous) story that it was used as a dungeon for the Christian slaves who provided labour for Moulay Ismail’s building spree. Bring a torch.