Moulay Ismail's reception hall for foreign ambassadors is a lovely show of zellige (patterned tile) work. It's here that Unesco officially inscribed Meknes in the World Heritage Site registry in 1996. In front of the building, small windows provide light for a 40-hectare crypt below. Descend via stairs to the right of the reception hall; 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. In the absence of anything much to see, tour guides often delight in recounting the erroneous but far more colourful fable that it was a dungeon for Moulay Ismail's slaves, and it's commonly labelled as a prison on maps.