At first it sounds like the low, distinctive groan of a pod of large whales. You half expect Sir David Attenborough to pop up next whispering into a concealed mic about bizarre sub-aqua mating habits. But it can't be. You are strolling on one of Croatia's most beautiful rivieras, in Croatia's student capital, Zadar, watching the sun dip below a vast archipelago of more than 100 islands.

You hear the whales again, this time in a slightly lower key. You scan the horizon over the crystal clear Adriatic, past dozens of white gajetas -- the small, wide-hulled wooden workboats of the region -- to catch a glimpse of the world's largest mammals. The channel between the town and the large island just offshore is busy with brightly-coloured flotillas of yachts, the last of the evening windsurfers and three enormous, yet vaguely ridiculous, mega-cruisers -- the type favoured by James Bond and men who own football clubs.

Could your ears be playing tricks on you? You were, after all, out quite late last night at Croatia's most happening club, The Garden, and the long lunch of a delicious seafood platter, washed down with local rosé, might just be making you a bit groggy. Then you hear it again, more melodious this time. This aquatic symphony seems to echo across the bay, bouncing off the islands of the archipelago.

The Adriatic might be home to more than 1,000 islands, it might have the cleanest waters in Europe, but unless global warming is having a serious impact on migratory patterns, it has never been known for its whale population.

As you approach the end of the riviera, the sound of the whales appears to come closer. Like all Mediterranean cities, dusk offers the locals the opportunity to stroll around, gossiping and watching the world go by. Zadar's palm-lined riviera is a place for people watching as black-clad grannies playfully admonish toddlers and some of the 8,000 students who attend the oldest university in Croatia, established by the Dominicans in the 12th century, flirt outrageously.

In 1964, Alfred Hitchcock claimed that "Zadar's sunsets are the most beautiful in the world -- more magnificent than California's". This evening, it is hard to argue.

The beauty of the sunsets has been complemented by a most spectacular, yet simple, piece of urban architecture. This bit of genius is responsible for the confusing maritime orchestra. A few years back, a local architect installed a 'sea organ' under the harbour. The organ consists of 35 giant pipes that are played by the waves. The sound is extraordinary and the organist is nature. The more wind and waves, the louder the symphony.

Zadar has always been an innovative and expressive city. For example, for four centuries during the dark ages, the human form disappeared in all art. It made its European reappearance in Zadar in the 11th century. As a prize, the city has been fought over by every invader, from the Greeks and the Romans before Christ to Milosevic's Serbs 15 years ago. In most cases, the invaders stuck around, contributing enormously to the local culture. Indeed, this tolerance of the Catholic Croatian city is best evidenced by the exquisite and still functioning Serbian Orthodox church in the old town, which still serves the small, ageing Serb population.

On a Sunday morning, I visited this incense-filled church. A bearded Orthodox priest, his back to the congregation, was leading his people through a beautiful Gregorian chant. To hear this so soon after the war, and in a conflict that was characterised by ethnic cleansing and forced evictions, is unusual in Croatia. But Zadar is different.

Maybe because this walled ancient city has been fought over for centuries, the locals have learnt to forgive and move on. So whether it was Napoleon using its great Catholic churches as stables for his horses, or the Venetians who razed the place with the connivance of the Crusaders, or, more recently, Mussolini who annexed the city and created the 31st province of Italy here, it seems that the people's capacity for reinvention is endless.

The Austrians also recognised its importance when they took the city from Napoleon, ushering in a golden age for Zadar and Dalmatia. An example of this prosperity is to be found just to the left of the main city gate, which is still watched over by the Venetian Lion. In front of the medieval citadel is a large ice storehouse, which was used by Austrian merchants who drank iced tea in summer. The ice was carried every day by mule from the huge, permanently ice-capped Velebit mountains, 30 miles away.

As befits this cosmopolitan city, the Austrians were replaced by the Italians, who were in turn kicked out by the Yugoslav partisans under Tito. Tito didn't have much regard for Zadar, finding it a bit too Italian for his liking. And so, under Communist rule, the former capital of Dalmatia had its first brief period of sleepiness and, given its history, it probably felt better to be ignored, rather than constantly coveted.

However, the peace was broken by the Serbs, who bombarded the city for three years in the early 1990s, leaving the citizens without water. Since independence, the place has flourished and the old mercantile spirit that made the city so valuable has re-emerged.

Today, this is a lively Mediterranean city ruled by Croats who settled here in the eighth century for the first time in more than 600 years.

At night, Zadar comes into its own with a plethora of trendy bars, cafes and restaurants. The hippest club, The Garden, is on the old town ramparts looking down over the Adriatic. Beside it is the impressive Arsenal Bar and Restaurant. The beauty of Zadar, with its marble, car-free streets, Roman colonnades and Forum, is that the ancient is fully integrated with the modern. Despite the age of everything, there is no sense of being in a museum. Cafes and bars are in these ruins, so you have as much chance of sitting on a piece of ancient Rome as the sun goes down as sitting on a piece of IKEA.

While the city of Zadar is attractive and special, the surrounding Zadar region is breathtaking. This area is the cradle of Croatian culture and all along the coast you will be amazed by the beauty of small walled towns made rich by salt. This is perfect salt country, given the shallow Adriatic waters and searing summer heat.

Both Nim and the island of Pag are well worth visiting. Nim is a pretty walled town with a moat around it, while the lunar landscape of Pag is extraordinary. In winter, a severe north-easterly wind called the Bora blows off the continental mountain ranges. It carries salt with it as it gains speed. Because Pag is the first mountainous island off the coast, large quantities of salt are deposited there. As a result, nothing grows, giving the island a barren, lunar surface. Pag is famous for its goat's cheese and decadent all-night raves.

For the more earthy types, the region sports three national parks. Paklenica mountain park (www.paklenica.hr) is the most famous, particularly with rock climbers. But as I suffer from vertigo, the idea of being half way up a cliff, clinging on for dear life, is not something that I was born to do.

This huge mountain range -- which separates the Mediterranean Dalmatians from the rest of the more Germanic Croats -- sweeps down to the sea at Zadar, making the coast a nautical heaven. Whether your weakness is for a small put-put to muck about in or a yacht flotilla to pit yourself against the Adriatic, this part of Croatia is perfect for anyone wishing to experience the magic of the Adriatic. Biograd (www.marina-kornati.com), with its impressive marina, is only about 15 minutes down the coast and, for salty dogs, would be a logical embarkation point for the islands.

From there, the Kornati Islands are only a short boat ride away. George Bernard Shaw was so blown away by the beauty of the Kornati that he wrote: "On the last day of the Creation God desired to crown His work and thus created Kornati Islands out of tears, stars and breath."

Zadar is perfect for a weekend break or as a base for a family holiday, either in the surrounding region or on the water. While the hordes descend on Dubrovnik, lovers of the real Croatia should avoid that tourist trap and head north to Zadar. The real, undiscovered old capital of Dalmatia awaits you.

- David McWilliams