I had seen pictures of Carcassonne and read how this French medieval walled citadel was the largest in Europe.

It all looked and sounded very impressive.

But no amount of research could have prepared me for the jaw-dropping moment I first set eyes on its walls and the realisation that this was going to be home for the next three days.

In a country that’s rich in castles, Carcassonne (or La Cite, as the locals say) is a contender for the most spectacular of all – because it has beauty AND brawn.

Over 4,000 men were once garrisoned within its double ring of impregnable ramparts dotted with over 50 barbicans and towers topped with conical roofs of silver and red.

It was the setting for the hit Kevin Costner film Robin Hood: Prince of Thieves.

And some of its magic rubbed off on Walt Disney, who stayed in the citadel in 1956. Three years later, the castle in the animated classic Sleeping Beauty bore an uncanny likeness to La Cite.

Carcassonne, in south-west France, between the Black Mountains and the Pyrenees, was first fortified by the Romans but most of what you see today dates from the 12th to 14th centuries.

This was a time when the citadel offered protection to the Cathars, a religious sect at odds with the Catholic church. In 1209, Vatican Crusaders laid seige and the ‘heretics’ surrendered after 15 days.

Carcassonne was never captured again. Indeed, in 1355 when the Black Prince, son of Edward III, swept through France during the Hundred Years War, he took one look and turned tail.

But its military importance gradually dwindled until by the 19th century it was in a state of decay. Incredibly, the French government of the day decreed that all the fortifications should be pulled down.

A campaign succeeded in saving La Cite and in 1844 architect Eugene Viollet-le-Duc began its restoration, stirring controversy by adding roofs to towers previously open to the skies.

Purists may moan that the citadel looks more like a Loire Valley chateau than it ever did in medieval times but they should be thankful to Viollet-le-Duc that it exists at all.

Today, La Cite is home to just 120 residents and welcomes over three million visitors a year, more than Windsor Castle and the Tower of London put together.

You can wonder the random network of narrow cobbled streets to search out bakeries, art studios, antique dealers and souvenir shops or watch the world go by at a cafe in one of the tiny squares.

You can stroll La Cite’s three kilometres of ramparts which are particularly romantic at night when bathed in gold light – and the crowds of day-trippers have returned to their home.

But the citadel is not just for couples, kids (especially boys) will love its torture museum, haunted house and endless supply of plastic swords to wield as they charge about the fortifications.

There’s also Musee de l’Ecole, a delightful little museum housed in an old primary school that shows how French classrooms looked 70 or 80 years ago, with flip-up desktops and fountain pens.

Plays, concerts, opera and ballet take place in the open-air theatre every July and there are medieval pageants, including jousting between the inner and outer defences, every August.

If you’re staying more than three days in Carcassonne you may want to hire a car and explore some of the other dramatic Cathar castles in the region.

One not to be missed is Montsegur, a modest fortress perched on a 3,000ft ridge, where 220 Cathars held out against the Crusaders for an incredible ten months.

In defeat, they chose to be burned alive rather than renounce their faith.

However, legend has it that several Cathars slipped through the Crusader lines carrying away a mysterious ‘treasure’ with them, said by some to have been the Holy Grail.

Carcassonne’s ‘lower town’ is worth a visit, too.

Known as Bastide St Louis, it was created in the 13th century when settlements below the ramparts were swept away for military purposes and their inhabitants forced across the River Aude.

Its grid of narrow streets was originally protected by solid walls, though little remains of them now. Markets are held in its central square on Tuesdays, Thursdays and Saturdays.

You can catch a barge at Bastide St Louis for a cruise along the Canal du Midi. Constructed in the 17th century, this 240km canal links the Mediterranean with the Atlantic Ocean.

Like La Cite, it’s a UNESCO world heritage site.

But the best reason to visit Bastide St Louis is to enjoy the wonderful panorama of the citadel – a breathtaking image that will stay with you forever.