The architectural heritage in the Loire Valley's historic towns is notable, especially its châteaux, such as the Château d'Amboise, Château de Chambord, Château de Chinon, Château du Rivau, Château d'Ussé, Château de Villandry and Chenonceau. The châteaux, numbering more than three hundred, represent a nation of builders starting with the necessary castle fortifications in the 10th century to the splendor of those built half a millennium later. When the French kings began constructing their huge châteaux here, the nobility, not wanting or even daring to be far from the seat of power, followed suit. Their presence in the lush, fertile valley began attracting the very best landscape designers and architects. The Loire Valley is an area steeped in history and because of its riches, one that has been fought over and influenced by a variety of adversaries from the Romans to Atila the Hun. The formation of the region as we know it today began after its conquest by Julius Caesar in 52 BC. It is however, Emperor Augustus who is credited with bringing peace and stability to the Loire Valley. This stability saw the growth of towns such as Orleans (Genabum), Tours (Caesarodunum), Le Mans (Noviodunum), Angers (Juliomagus), Bourges (Avaricum) and Chartres (Autricum). The Roman's greatest influence however might be considered to be the introduction of the first grape vines to the region, as shown in the wine AOC map shown above.