Why is the riad so hard to find?

Because a medina address is not really an address — it's a set of nesting dolls. Derb Moulay Abdelkader n°7 means: find a dead-end alley by name, then find a number that exists only inside that alley. Number 7 lives again in the next derb, thirty meters away, entirely unbothered by the coincidence. There's no grid, no sequence, and the entrance to the derb itself is often an unmarked archway between two shops selling identical slippers.

GPS, bless it, makes things worse. The signal drifts ten to twenty meters between four-story walls, and the map often shows a wall where a passage is. The blue dot will place you, with total confidence, one derb over — on the wrong side of a two-meter-thick earthen wall you'd need ten minutes to walk around. Why the GPS lies is its own entry.

The system worked for eight centuries because addresses were social, not cartographic — you asked for a family, and the neighborhood walked you there. Riads know this, which is why the good ones offer to meet you at the nearest landmark. Take the offer. It isn't an upsell; it's the address working exactly as designed.