Castello Baronale is the ultimate Dolce Vita film-star retreat. You survey the world but remain invisible. There are only two ways of entering - over a drawbridge or through a pair of automatic wrought-iron gates that open on to an arrow-straight cobbled ascent enclosed by neatly clipped hedges.

Better still, you are just 50km (30 miles) from Rome, though after you leave the motorway the last 10km are a steep, winding ascent to a 900m (3,000ft) acropolis. The final approach circling through the streets of the village of Collalto Sabino (literally, “high hill of Sabino”) to the castle gate makes you feel like a prince.

Ian Zammit, chief officer of the property division of Global Capital, which owns the fortress, welcomed me into the castle courtyard, saying: “You can see 32 villages from here.” This seemed a little optimistic because the castle was enveloped in mist, but suddenly the sun broke through and I glimpsed a farmhouse perched on a nearby hilltop. Moments later, line after line of hills and mountains came into view, with villages visible 20 miles away.

Global Capital, which is based in Malta, bought Castello Baronale three years ago and is now selling it for €11.5 million (£8.95 million). For this you get a mountain-top domain of 17 acres and not one but two castles. The first, containing the living accommodation, is in excellent condition. The second, upper castle is a geometric Renaissance artillery fortress with a central keep, battlements and circular corner towers for cannon. It's every boy's dream.

Castello Baronale comes with a spectacular pedigree. Over the drawbridge entrance is the coat of arms of Cardinal Francesco Barberini, one of three judges who refused to sign Galileo's sentence in the Inquisition. In the Middle Ages the castle was held by a series of great Florentine families - the Savelli, the Strozzi and the Soderini. In 1798 the rich furnishings were looted by Napoleon's army. Worse followed in 1861, when the castle was sacked by Bourbons from the Kingdom of Naples contesting Garibaldi's drive to unite Italy.

By the early 1990s the castle had come into the hands of the Rinaldi family. Count Maximus Rinaldi invested heavily in it, restoring it as an exclusive and luxurious hotel.

Zammit says: “He sold it to us because his children didn't want the burden of looking after the place. We started with a few paying guests but you can't run a profitable hotel in a place like this with just ten rooms, so we switched to weddings.” Catering is organised by an excellent local restaurant, L'Angolo d'Abruzzo.

The castle is booked almost every weekend in June and July but Zammit hopes to sell it as a private house. “Consultants advise us that now Tuscany prices are so high, Lazio will follow and this property will be worth €20 million in a few years. But we are investors and want to sell.”

The entrance hall retains a Baroque stone fireplace and stone doorways. The vaulted lower chambers are perfect for large candlelit dinners. Above, lofty interconnecting salons allow you to remain cool in summer. The showpiece of the castle, though, is the double-height great hall with a 30ft-long Baroque canvas of Moses dividing the Red Sea. There is also a self-contained owner's apartment with a large living room and two double bedrooms with views over the village below. The Milanese architect Rodolfo Dordoni has produced a dramatic scheme for transforming the upper castle into the ultimate hedonist spa with swimming canals beneath the vaulted galleries and indoor pools on three levels. As we enter the upper castle we hear the sound of gushing water beneath the floor of one of the towers - it turns out to be an unending supply of mountain spring water.

The views up here beat those from the Hollywood Bowl by a factor of ten. The so-called Valley of the Knights extends for miles below, while immediately in front of you the bell tower added by Cardinal Barberini jostles picturesquely with the tower of the parish church.

Castello Baronale comes - if you wish - with a staff of two who have been here for 20 years (Giuseppe has a farm near by and brings fresh eggs every day). But you must also make common cause with the villagers, whose Easter procession winds through the outer ward of the castle. Your mission as the new owner is not just to relax by the pool and play tennis but to defend the beauty of this place as valiantly as your predecessors over the past 1,000 years.

WHAT YOU GET: Nine bedrooms, three drawing rooms, great hall, conference room, gatekeeper's cottage, taverna, owner's apartment, swimming pool, tennis court. In all, 7,000 sq ft.

WHERE IT IS: 50km (30m) from Rome in the mountain-top village of Collalto Sabino (population 500) on the borders of Lazio, Abruzzo and Umbria.

AIRPORTS: Rome Ciampino (easyJet) 55km; Rome Fiumicino (BA, Alitalia) 80km.

PRICE: €11.5 million (£8.95 million) via Knight Frank, 020-7629 8171, or Carol Anastasi, 00 39 333 779 9761.

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