Nearby are a couple of interesting Byzantine churches co-opted as mosques. To the south is the Bodrum mosque which began as the Monastery of Myrelaion. To the north is the Kalenderhane Mosque, originally the Church of the Theotokos Kyriotissa.

The Tulip Mosque looks out of place here, sitting amongst cheap electronics shops. A big, cream coloured stone lump, built in the eighteenth century and about as Baroque as a mosque can get. Going through the gate is peaceful and makes Laleli seem even more Eastern. It doesn't feel jarring like some of the other mosques where you pass from a modern, European city into an old, Arabian tradition.

Beneath it is a bazaar. Small and scruffy, catering to the locals, immigrants from the Balkans or central Asia. I've never appreciated how "holistic" mosques are. In Europe, the grand cathedrals were not for the likes of you and me. They were for the nobility to show you how wealthy and powerful they were. You were not wanted there, you might be able to buy a ticket and wander round now but a couple of centuries ago they'd be shoving hot irons in your eyeballs if you'd even set foot near it.

But mediaeval mosques, as grand as any European cathedral, had markets and soup kitchens and schools. They were centres of the community, not exclusive religious country clubs for the nobility. I'm not going to go all apologist, Islam has huge problems and the Ottomans were particularly brutal, but it was an eye-opener to see how egalitarian and socially minded mosques were. Interesting to note, in all of the mosques I visited in Istanbul not once was I asked for any money. Even in the most important or significant, if the doors were open then you were free to come and go. Pretty much every historic church you visit in Europe will either make you buy a ticket or guilt-trip you with a collection box. Apart from the Haghia Sophia and St Saviour in Chora (now both technically museums), I never once had to pay. I guess it is one of the great paradoxes that Islamic culture is rooted both in hospitality towards strangers and exclusion of outsiders.

Back out to Cemberlitas. The Burnt Column. Built by Constantine and allegedly housing relics in its base, the column was blackened by a fire in Ottoman times. This marked the start of Roman Constantinople. From here onwards, the great Roman road led east into the heart of the Imperial city. Now it marks the best entrance to the Grand Bazaar. It leads past mosques and mausoleums to the Nuruosmaniye Gate. Pass this and you are in another world.

Like I said, I am ambivalent about the Grand Bazaar. It was enough for me to stick my head in for ten minutes. Streets and streets of shops selling exactly the same thing. Painted bowls, glass mosaic lamps, spices and leather. There is the occasional merchant selling something unusual but most of it is the same stuff over and over. Which is also for sale elsewhere in Sultanahmet, in the Arasta Bazaar, in the streets behind the Blue Mosque, in the airport tourist shops. It's nothing you will not see anywhere else. If you want to buy, great. If you don't, not so great.

But I like seeing how places like this work. I don't really care about what's on sale. I like watching the little guys running round with trays of tea for the merchants. How does the guy keep track of who drinks how much tea? Is it free? The whole place is a small town, self-contained and insulated from the rest of the world. There are traditions amongst the merchants that you get little glimpses of if you take your eyes away from the junk for sale. All the support workers, the people sweeping the floors, all the people who keep the place running. It's own little mosque so the merchants can meet their religious obligations. That is what fascinates me. The mechanisms and that whole world behind the shop window. The hans where stuff is made.

Istanbul is a city that teaches you to be rude. Every merchant looks for that moment of weakness. Eye contact or lingering to look at something. They are ferocious and relentless. You absolutely cannot stop moving in Istanbul and especially in the bazaars. Don't meet their smiles, don't respond to their greetings. To a westerner, that is not easy. But after a day or two, you stop caring about being rude because otherwise you never get anywhere.

Maybe that is why I didn't look in the windows. I liked looking up. The roofs are interesting. Ottoman eagles. Signs you didn't notice. Stairs that lead to places you do not get to know about. There are colonnaded squares where you can escape. Cafes. The marble paving is treacherous and the place is a labyrinth. Do not go to the Grand Bazaar and waste time looking in shop windows. It is the stuff all around that is fascinating.

I escaped. Back out what I thought was the gate I came in but I was in a different place. Back streets. Each street sold something different. One was pots and pans. Round the corner was a street entirely of shops selling very functional women's underwear. Steep hills. The sky a distant slice of blue as buildings crowd in on you. Climb another hill and I was back at the Grand Bazaar.

Turn around.

A shortcut down an alleyway and now I was in a crumbling courtyard. The walls were a series of stone arches like cells in a beehive. Overgrown with bushes and the crunch of broken glass underfoot. This was a han, one of the old centres of commerce where horses and mules were parked, where craftsmen worked, where merchants counted their coins and made trades. Today hipsters would call this a "hub" like they invented something new. In the east, this was daily life for centuries.

Climb another hill, another cobbled alley. Pass a gate and think that I've ended up back in the Grand Bazaar again. I was getting tired when it opened out on to a plateau topped with what I think is the most beautiful building in Istanbul..

I did not know it was there. It came as such a surprise that I had to look it up to find out what it was. In amongst all the chaos and commerce and moneymaking, a beautiful, peaceful complex of graceful buildings and gardens.

I entered by the cemetery. Hooded crows perched amongst the gravestones, carved pillars all jumbled together like something organic. Maybe a forest. The octagonal mausoleums of Suleyman the Magnificent and his Russian wife, Roxelana, sat quietly as though they were summerhouses in a garden.

Europe had almost fallen to Suleyman. The Ottoman Empire had reached its peak under him and covered Hungary and Greece and the Balkans. North Africa was his, too. The Christian world was hemmed in west of Vienna and feared for its survival if Vienna fell. To the Turks, he is probably the greatest hero after Ataturk.

I wandered round the gardens of the mosque complex. On the other side is a terrace that looks out over the Golden Horn and the Bosphorous. Europe and Asia laid out in front of you. Right here, in the commercial centre of the Ottoman world, you can watch ships come and go with cargoes. You can see two continents and know you owned half of both. This was a seat of power and Suleyman, or at least his architect, Sinan, created gardens and tranquility and elegance. The Suleymaniye is not the Trump Towers like the Topkapi Palace is. Ottoman architecture can be gaudy and ugly and tacky. Or it can be beautiful, like this.

I walked round, stopping for a piss in toilets that looked like monastic cells. Sinan's own tomb sat at the far end of the complex, distant from Suleyman and the rest of the royalty. I kind of think he got the best spot for himself.

I crossed through the gardens and into the courtyard of the mosque. It soared up like a big, white mountain. Tumbling domes, copied from the Haghia Sophia. The columns of the courtyard came from the remains of the Hippodrome. It was empty apart from a couple who looked European. The woman, dressed overly fashionable and with a constant pout, posed amongst the columns. Her boyfriend chased after her, photographing her and being shouted at for not doing it right.

I headed down the hill towards the Golden Horn. The streets were steep, I felt like I was tumbling down towards the water. I was falling downhill. Through the street of the ironmongers then into the street of pot and pan sellers. Rows of shops selling sledge-hammers and angle grinders, turn the corner and everyone is selling rolling pins and sieves. How different was it in Ottoman times when every street was a different trade?

Down. Streets so steep the pavements turned to staircases. A glimpse of the sea then back into commerce and trade again. Down and down some more.

More bazaars. One selling pets. Hamsters and birds and cages and straw. Another bazaar selling plants and garden stuff. This is how the world looks without suburban retail parks and chain stores. You come to the market, you talk to the guy who owns the stall. Don't like what he sells? You go to the next stall. The guy who takes your money? He's the guy who keeps it. Not some board of directors or shareholders or pension fund.

And then into the Egyptian Spice Bazaar. I liked this, a lot more than I liked the Grand Bazaar. The smells, the sun coming through the dusty air. Crowds, some elegantly dressed in their Saturday clothes, some in headscarves or cloth skull caps. The Grand Bazaar was as much a tourist show as anything else, the Spice Bazaar was a working market. I wandered round, stopping for coffee and baklava at a little stall.

In amongst it was another mosque. The Rustem Pasa. Easily missed, a doorway with stairs leading up to a hall that sits above the market below. Paid for by rents from the stallholders, Rustem made a lot of money from the market. Maybe he built it high up to distance himself from the way he made his millions.

Out into the sunlight. The waterfront at Eminonu. People everywhere, eating fish sandwiches and drinking pickle juice. A sunny Saturday afternoon, talking and laughing and eating. I did the same and sat looking out over the Golden Horn. I stood up when I was finished and turned around.

It stopped me dead. The whole skyline was a mass of domes. It looked unreal, a forest of giant mushroom caps. The highest was on the Suleymaniye mosque and they spilled down the hill.

I walked round the waterfront. Crossed the Galata Bridge. Anglers, all men, elbow to elbow on the rail of the bridge. Two or three rods each, lines dropping into the blue water. I looked over the rail and the water was clear. It surprised me, I expected it to be filthy but you could see jellyfish and the occasional silver flash of mackerel. Halfway across I dropped down the stairs to the lower level and walked back. Once it had been lined with tea houses but these had been replaced by fancy fish restaurants. Women with too much makeup and bleached blonde hair sat and smoked while men stared at their phones.

The sun was setting and the last call for prayer sounded. I stood in the courtyard of the New Mosque as the crowds poured past. Like everything around the Spice Bazaar, it seemed a bit grimy like a place that had been well used.

A protected harbour, the meeting of two continents and the end of the Silk Road made Istanbul the perfect place for trade. Europe had the Americas but the Ottomans still held the gateway to Asia. The Bazaar Quarter would have been the beating heart of all that commerce. It is industrious today but it must have been even more so in Ottoman times. You can see how much wealth there must have been in the mosque building. I don't think the sultans built anything small. Even in the Byzantine era, Venice, the other great trading culture, coveted Constantinople and invented a crusade just to get hold of it. When it became Ottoman the sultan stopped just being the dude who owned the goods. He owned the markets, he owned the harbours, he owned the roads. He had it made.

I think the Grand Bazaar really only exists today for the tourists, it did not seem a place where locals went to shop. The real trade, that seems to go on in the streets around it. The Spice Bazaar, and the smaller bazaars nearby, really were still vibrant. No marble paving here or street-sweepers or tea waiters. As much as I hate shopping, the Bazaar Quarter is a fascinating side of Istanbul. Apart from the clothes, the bad music and the glass shop-fronts, probably not much has changed here in centuries.