Net profits: To get the true flavour of any city in the world, head to its fish market

Living in Venice, people often ask me where is the real centre of the Serenissima, and then look surprised when I say the Rialto Fish Market, rather than the Piazza San Marco or Doge's Palace. The pescheria is where all of Venice meets, to shop for the freshest fish, have a glass of prosecco, gossip about football and the latest Berlusconi scandal.

It is a snapshot of typical daily life in a very atypical city. And whenever I arrive in a new city on my travels, I stash away guide books with their must-see advice, ignore the travel blogs, and instead just ask where the local market is, and head straight there early the next morning.

Whether it's Marseilles or Bangkok, Marrakesh or Kuala Lumpur, you are immediately immersed in local colours and smells, culture and religion, cooking and food.

First stop whenever I visit Barcelona has to be La Boqueria, where right in the heart of what many claim is the world's greatest market, are the fabulous fishmongers, perfectly-coiffed ladies who put as much effort into the way they look as the presentation of their cornucopia of fish, regally presiding over a dazzling array of squids and crabs, razor clams and oysters, anchovies and sardines. The beauty of the Boqueria is that after this visual feast you can grab a stool at one of the market's many tapas bars and taste the freshness of the fish and seafood for yourself.

It's the same in Istanbul, where one side of the Golden Horn has a bustling fish market, specialising in locally-caught palamut (bonito), mackerel, sea bass and bream, displayed in the Turkish style of turning out the red gills. Then wander across the Galata Bridge to where an enticing smoky aroma rises from a flotilla of small boats moored on the quay, busily grilling the most delicious mackerel you have ever tasted, served in a fat sandwich with raw onions and peppers, and eaten squatting down on a tiny stool.

Recent trips have taken me to an amazing fish market in one of the faraway islands of the Azores, where cuttlefish and moray eels grow to quite frightening proportions in the deep Atlantic waters. I was surprised to come upon an ancient marché aux poissons hidden away in the backstreets of Saint-Tropez that seems stuck in a Brigitte Bardot timewarp, where glamorous shoppers vie to buy glistening red mullet and snapping lobsters direct from local fishermen who only brought the catch home that morning.

While further down the Riviera, in glitzy Cannes, I quickly escaped the faux-chic of La Croisette and plunged into the teeming crowds that fill the Marché Forville every morning, where much of the seafood is still wriggling on the ancient marble sinks. The fishmongers compete to show off the most colourful selection of prehistoric-looking poissons de roche that are soon to be transformed into a delicious bouillabaisse.

In the steamy, narrow lanes that climb up Hong Kong island, I thought I'd discovered the ultimate street market, where the fish look more alive than in the sea, laid out on the pavement in scores of plastic buckets, with seriously weird molluscs and crustaceans that most people would think twice about before ordering in a restaurant.

But then I arrived at Sai Kung in the New Territories, where the fish stalls are actually installed on tiny boats bobbing in the water below the quayside. Diners precariously lean over, choosing from giant prawns and whelks, crabs, abalone and mantis shrimps, which are then dispatched to the kitchen to be prepared for lunch.

The most surprising fish market I came upon was on a trip this year to Bangkok, where there wasn't a live fish in sight. This is because the Tatien is a specialist dry-fish market, which – thanks to the smell – you realise before you've even walked in.

Wandering down the narrow aisles, the displays resembled a series of abstract paintings as, dried-out and often preserved in salt and herbs, the fish are arranged in graphic lines and circles.

I certainly won't find anything this exotic when I go over to the Venice fish market today, but every market around the world has its own special delicacies, and not many of the tourists on the Rialto will have any idea how delicious the local soft-shell crabs are, or just why there's a crowd trying to buy the ugly "go" fish from the muddy lagoon, which are actually the secret ingredient in the "brodo" broth for a risotto di pesce.