The assault begins early, before dawn. The call to prayer shatters the medina's fragile peace, the amplified sound rushing over rooftops, sweeping along deserted alleys, tearing through barred windows and into the bedrooms of the slumbering public.
There must be more than one mosque close by - it sounds as though the muezzin, those doing the calling, are all trying to outdo each other with their enthusiasm, maybe in the hope that the most fevered cry of "Allahu akbar!" will attract the most worshippers.
One starts up, then another distorted voice, then another, and another. The air vibrates. The city stirs. To the sleep-addled tourist it doesn't just sound like a general call to prayer; the stream of Arabic seems to go on for so long that you can imagine each worshipper must be being called out by name.
"Hassan, time to get up!" they call from the minarets. "Ismail, wakey wakey! Fatima, give him a poke, get him going!"
It probably only lasts a few minutes but it seems to last forever, before eventually the muezzin are satisfied with their work and silence reigns once more in Fez.
Time to go back to sleep and prepare, because the true onslaught hasn't even begun.
Some cities are quiet, circumspect. You can spend days and days in them without meeting anyone, without having a conversation more meaningful than "one coffee please". It takes effort to get to know people. It can be a lonely experience.
Fez is not one of those cities.
Bab Boujloud marks the physical beginning of the attack, if not the aural one. The "blue gate" is an entry into the ancient medina, and a foreign land. Visitors are welcome, but they won't feel at home.
You don't know where you're going. You might imagine you can trek these ancient, winding pathways on your own, but you're wrong. Stray off the main alleys for a few seconds and you'll be hopelessly lost, doomed to wander between narrow, crumbling walls for the rest of your existence.
Fortunately that's never going to be a problem, because before you've even considered striking out alone you've found a friend. No, you've found two friends. Wait, three.
They hang around by the gate, these guys, waiting to clock tourists like you attempting to tackle a place such as Fez on your own. You can spot them out of the corner of your eye as they break away from the pack - fighter jets with missile lock, drifting in behind you and preparing for the best moment to strike.
This is usually when you first pause to consider where the hell you are, which is usually within a few seconds of stepping into the twisting warren of tiny alleys that is the medina.
"My friend, where are you going?" It's a kid. He can't be more than 14. "Do you need a hotel? I can get you good hotel, warm shower inside room, 150 dirhams."
You shake your head. "No, I've got a hotel."
"Then you need a tour? I can take you to the tannery, find good restaurant."
You might refuse again here, but that won't deter your new friend. He'll patiently tail you, waiting for the streets to engulf you, waiting for Fez to overwhelm you. Then he'll strike again.
The assault comes from every side. You're assaulted by animals: by the donkeys and mules trundling through the alleys laden with their wide loads of produce; by the stray cats hanging around the fishmongers looking for scraps; by the "free-range" chickens that cluck around, blissfully unaware that a swift nod from a shopper will bring about their ultimate demise.
You're assaulted by people: by the workers trying to push their carts through the dense crush of bodies in the streets; by the local shoppers trying to secure tonight's meal; by the smiling, mustachioed faces of the purveyors of olives and bread and cow hooves and fried spleens and saffron-roasted chickens and lovingly crafted sweets.
There are smells of spices, smells of donkey poo, smells of wood smoke, and the tang of semi-cured animal skins that wafts in from the tannery. The scene is shot in Technicolor, from the food stands to the locals' hooded gowns (djellabas), to the stacked displays of medicines and spices.
The melon sellers call out their specials. The chickens cluck and squawk. The workers yell for people to clear a path. The shoppers haggle over chunks of meat.
Your would-be guide waits patiently for you to bow to the inevitable and hire him.
A day in the Fez medina feels like a week anywhere else. And it finishes much the same way it started: with you ensconced in a hotel somewhere, relaxing, unwinding, when the air is shattered with a haunting, familiar sound: the call to prayer.
Have you ever been overwhelmed by the sights, sounds and people of a city while travelling? Post a comment below and share your stories.