And just like that, you're lost. Hopelessly, wonderfully lost.
It's merely an archway for an entrance, a dark gap in the wall with a steady stream of people moving in and out. They shuffle through, clutching bags, mostly keeping to themselves. There's no sign or billboard to announce the presence of what lies beyond, but everyone knows.
The bazaar is a tourist attraction that's not a tourist attraction at all.
You make your way towards the archway and step inside, letting your eyes adjust to the gloom, taking a while to register the new environment. There's a small electric sign with something written in Farsi. There's a domed roof that stretches on into the darkness. Everywhere else, there are people.
Some call out from shops and stalls. Others gather around to handle merchandise and haggle with sellers. Some push wheeled trolleys through stone corridors. Most just hustle through the middle, robed figures dragging children or hefting bags of goods.
This is Esfahan's main bazaar, a centuries-old warren of shops that sell just about anything you could ever desire to get your hands on (except, of course, alcohol). From dark bolts of cloth to fake designer jeans to spices, jewellery, electronics and carpets - it's all within this dark series of vaulted hallways that bends and twists through central Esfahan.
The bazaar is a tourist attraction that's not a tourist attraction at all. It's the beating heart of the city, a working market devoid of kitsch or tacky traps. There's no hassle from pushy salesmen and no pressure to spend up on trinkets. It begs to be explored and observed.
There are several dangers, however, in entering an Iranian bazaar - not least of which is spending the rest of the day with the OMC song How Bizarre stuck in your head. The next most frightening scenario - and equally likely - is getting lost.
Just like its counterparts in Tehran and Shiraz, the Grand Bazaar in Esfahan is fiendishly difficult to navigate for first-timers, a labyrinth devoid of landmarks or signs, a maze that requires an incredible sense of direction to successfully traverse.
Such an incredible sense of direction, in fact, that you soon give up trying. And that's when you really start to enjoy yourself.
You might not know where you are, but the dark stone corridors soon start to make sense. The shops become recognisable, and their owners become recognisable. Most of all, however, you become recognisable, because they're aren't many tourists in this town, and a white face always registers.
"Hello Australians!" one vendor smiles, leaning on a rack of fake designer jeans. "Welcome back!"
You see normal Iranians doing normal things here. There's a group of women going through bolts of black cloth, each style flecked with a subtle pattern, a small show of personality. The women themselves are robed, although the jeans and high heels poking out the bottom hint at something a little more risque.
There are five or six mullahs sitting on small chairs, having a chat. The call to prayer erupts and they don't even break conversation, they just keep speaking and gesticulating, no doubt solving the problems of the world - or maybe talking football. Um, guys ... Mosque?
Down a quiet alley there's an old man perched on a hessian sack, singing his own call to prayer, a haunting warble that ripples across the ancient walls of the bazaar. The guy across from him selling sugar, these huge stacks of fat yellow crystals, pays little attention, unaffected by the simple beauty of the moment. He's probably experienced it every day for years.
Iran is strangely devoid of restaurants but there's one in the bazaar, a tiny little place that seems to have been burrowed out of the old wall. Skewers of meat are sizzling over hot coals; the lady out the front is stirring a huge vat of thick eggplant soup.
You're directed upstairs to eat, climbing a narrow spiral staircase to a room with an arched, tiled roof, the heat from the coals below wafting through cracks in the flooring. You sit down and eat as a normal Iranian would, tearing at bread with your hands and wrapping it around bits of grilled meat and tomato.
Then you wander back into the fray of the bazaar, back through the dark corridors lined with produce. Circles of sunlight on the stone floor show that it's still daytime but there's no other sign to indicate where you are, or what's happening in the outside world. And it really doesn't matter any more.
Is getting lost when travelling always a bad thing? Has it happened to you? Leave your comments below.