Moored in the bluest Mediterranean waters, this often-overlooked Italian island is home to enchanting coastal towns, superb diving spots, Roman ruins and incredible cuisine.

Despite being part of the same country, Sardinia is fiercely distinct from big-booted Italy and its volcanic little brother Sicily. The wildly colourful island is located as close to Tunisia as it is to mainland Italy and nearly grazes the French island of Corsica. It is moored in the bluest waters of the Mediterranean and is home to superb diving spots, Roman ruins and some of the most memorable cuisine in southern Europe. With African-tinged flavours, a language all its own and a very peculiar take on cheese, Sardinia exudes an independent spirit.

Well-heeled visitors will make a beeline for the glassy waters of Costa Smeralda, but this unique island has more to offer than its achingly beautiful seas. These three enchanting coastal towns form a worthy road trip from the island’s northwest to its south.

Alghero: Relics, shopping and the bluest of grottoes
Alghero has sun-baked streets, medieval archways and is a stone’s throw from fine sandy beaches, making it a magnet for Italian tourists. The oceanside town also offers clearer waters than its name suggests (inspired by the Italian word for seaweed, “alga”). Shop in the boutiques along Via Roma, be dazzled by displays of red coral jewellery and tread cobblestoned streets to admire the Gothic details of Cattedrale di Santa Maria. Reward your efforts with mouth-scalding fresh pizza or saffron-tinged seafood risotto in one of the Old Town’s bustling eateries.

For culture, the Museo Diocesano d’Arte Sacra near the cathedral is splendidly austere and harbours some ghoulish relics. The dainty skulls of the innocents slaughtered by Herod are neatly displayed in ornate cases, and stunning silverwork entombs a fragment of the “True Cross”.

But it is the natural sights nearby that really put Alghero on the map. The Grotta di Nettuno at Capo Caccia, a goblin kingdom of eerie rock formations, dripping stalactites and winding caves, is a blindingly blue excursion about 45 minutes away by car. Signs from Alghero direct you to a tiny car park and then down a craggy staircase to the caves. Those with no head for heights can take a boat ride from Alghero directly into the mouth of the grotto during the summer months. Guided tours are available.

Oristano: Battle-torn history and matchless cuisine
A couple of hours’ drive south of Alghero is the historic gem of Oristano, a coastal town that looks serene but has a bloody heritage of vicious Saracen attacks.

The town today is all understated loveliness, with azure waters and pastel-coloured waterfront houses. Wander to the remains of the old city at the Torre di Mariano II, a fortress in Piazza Roma, and stroll through quiet streets to a statue of the island’s heroine, Eleanora d’Arborea, on the piazza named after her. This formidable noblewoman composed a heavyweight body of laws that held fast for hundreds of years after her death in the early 15th Century.

Discovering the history behind this city works up a serious appetite, and you should not leave town without trying Oristano palate pleasers, like bottarga antipasti (cured fish roe) and gnocchi served with spinach, eggs and cream, all washed down with the famous local wine, Vernaccia di Oristano.

One Sardinian delicacy is such an acquired taste that you will be relieved to know it is hard to find outside the black market. Whiffy Sardinian sheep’s cheese casu marzu is so ripe it is crawling with maggots. The squirmy vermin are eaten along with the cheese, and it is hard to be sure whether it is the chewy addition of maggots or the eye-watering odour of the cheese that enhances its reputed aphrodisiac properties.

Cagliari: Roman ruins on the Gulf of Angels
From Oristano, Cagliari is an easy 90-minute drive south or about an hour by train. The slick but scenic city is nestled in the Golfo degli Angeli, a curved bay nestled in Sardinia’s southernmost edge.

Cagliari has a far more cosmopolitan feel than its northerly neighbours. Shady shopping arcades and trendy dining enclaves are the norm along Via Roma and Largo Carlo Felice, yet the Castello district remains unspoiled and Roman ruins (including an amphitheatre) are dotted throughout the city.

If shopping does not sap your strength, test your thigh muscles by ascending to Cagliari’s crowning glory, the Bastione Saint Remy, to get soaring views over the city. Head back down into the Castello district – a maze of medieval alleys – to admire the imposing facade of the 13th-century Cagliari cathedral.

After days of dusty sightseeing, your final stop is the sea. Recuperate in the waters of Poetto beach and dream deeply on its white dunes.

The article 'Sardinia's island splendours' was published in partnership with Lonely Planet.