A further surprise is that this distinctive collection of buildings wasn't converted into a hotel until 2009. Before that the estate belonged to a celebrated Tuscan winemaker, Lionello Marchesi.
But for 900 years it was owned by the aristocratic Chigi family, who produced a couple of popes and whose family home in Rome, the Palazzo Chigi, is still the official residence of the Italian Prime Minister. Men of wealth and influence strode across this splendid central piazza even before the arrival of Gordon Ramsay.
But Gordon is not the only famous name attached to Castel Monastero. The hotel has also signed up Dr Mosaraf Ali to oversee the sumptuous spa, enabling it to trade on Dr Ali's reputation for combining traditional Indian and Western medicine to achieve great and profound things, such as getting the Duchess of Cornwall to give up smoking.
Reintegration of mind, body and spirit is Dr Ali's credo, which would doubtless have pleased the original monks, who built the place even if they might've baulked at the cost.
I dare say they would also have approved of the rigorous marma massage I was given by a wiry little therapist called Roberta. She was trying to promote good blood flow by stimulating my marma points (the 107 neuro-muscular junctions where veins, arteries, tendons, bones and joints meet).
Whatever, Dr Ali's methods have had widespread celebrity endorsement, not least from Morgan Freeman, who goes to Castel Monastero for treatment to the nerve damage he sustained in a car accident four years ago. And, doubtless, for the food, wine and tranquillity too.
LOCATION
Castel Monastero stands on a hilltop south-east of Siena, appealingly off the beaten track but close enough to the main road to Arezzo.
Like practically everything else in this lovely region of gently rolling hills, the cypress-lined main road itself could illustrate the front of a tourist brochure - or could but for one regrettable feature: the women standing at the roadside every 300 metres or so were not, in fact, hitch-hikers.
The hotel's charming manager clapped a hand to his forehead when I mentioned it; he has written to the council more times than the Australian guest moaned about his wife's starter. The manager cheered up, however, when talking about Siena, which he said, "Was built to celebrate the majesty of God... whereas Florence was built to show off''.
Castel Monastero is well placed for trips in and out of one of Italy's most unspoilt medieval cities and the hotel even has its own apartment overlooking Siena's Piazza del Campo, complete with balcony for the best-possible view of Il Palio, the horse race held there twice every summer.
COMFORT
The 75 bedrooms are mainly around the piazza, though we stayed in a simply but lovingly furnished suite in a converted stable. We used the two bottles of free local wine to toast the donkeys who'd lived there before us in an age that was not entirely donkey-friendly. (The Florentines, during their regular sieges of Siena, used to catapult them over the walls.)
There were Molton Brown products in the bathroom, and every modern convenience, including free wi-fi, a huge wall-mounted televisions in bedroom and sitting room, and a proper fridge.
The service was impeccable and there was a swimming pool and floodlit tennis court if we needed them.
- INDEPENDENT