When a medieval warlord built the granite and brick fortress standing guard over the hilltop town of Montalcino, he meant it to be an impregnable obstacle to invaders. The modern town fathers of the noted Tuscan wine centre had a better idea: they transformed the 14th century ramparts into a tasting room. Where rival factions of the renaissance power game once clashed with broadsword and halberd, visitors can now sip a nicely-balanced brunello. The soft red wine of Tuscany flows pleasantly where the blood of English mercenaries and Teutonic knights once ran across the granite flagstones. Etruscans made wine in the valleys of Orcia, Asso and Ombrone long before the first tribune ruled Rome. In a circle 16 kilometres wide around the hilltop town, hundreds of wineries still produce vintages made from the deep purple brunello grape. This is the mother vine of Italian wine; elsewhere, like 70km up the road in Chianti, it is known as sangiovese. But scientists and farmers have carefully cloned the vine so the fruit it now produces is different - and makes a completely different wine than anything tasted by the Caesars. Although the wine region is comparatively small, complex local geography creates scores of tiny micro-climates. The upthrust volcanic ridge on which the fortress was built is flanked by sandy soil with strains of limestone. Some south-facing fields catch the blazing autumn sun, others are sheltered from sudden rains. The result is a huge variation in wines, made even more complicated by different pruning methods and winemaking techniques. So when an exporter ventures into the tasting room, he is confronted by hundreds of contrasting wines, all made from the same grape variety grown in the same confined region. There are more brunellos than you can poke a pike at; hundreds of versions line the granite vaults of the old fortress. Each bears its own label, and most Montalcino wines have a soft, gentle nature. They can be enjoyed with chicken and other light dishes as well as hearty roasts. With spaghetti and a meat sauce, you're in heaven. The local wines once made burly, strong reds. Then, in the last century, local landowner Ferruccio Biondi-Santi carried out pioneering genetic work and gentled the powerful native grape. The result is a sophisticated, subtle product which Italians like to call 'the first designer wine'. Biondi-Santi was a revolutionary in more ways than one. He marched with Garibaldi the length of Italy to unite the country for the first time since the end of the Roman empire. With that victory won, he turned his talent to changing the nature of grapes. There was nothing subtle about the vintage knocked back by the well-armoured Duke of Montluc in 1533 as he readied his vastly outnumbered troops of the Republic of Siena to confront the invading Florentines. History records 'he reddened his face with a robust vermilion wine' as he took to the ramparts to do battle. By the 17th century, with a semblance of peace in the peninsula, tourists and pilgrims tramped through Tuscany from Northern Europe on their way to Rome. Inevitably, they tried the wine of the country. Equally unavoidably, they took some home. William III of England demanded the softer Montalcino wines instead of the Bordeaux reds which had been traditionally favoured at Buckingham Palace. He probably would not recognise a modern brunello.