The best-known contributions to architecture by the French in this time are their famous châteaux. The typical example of these is the Château of Chambord, commenced by Francis I immediately after his return from his Spanish captivity. While the design is classical in detail, it is eminently French in character, and it has been a favorite study of architects ever since. Its repute shows how well architects at this time {131} accomplished their purpose of making an impressively beautiful building. At this same time the Château of Madrid, situated in the Bois de Boulogne at Paris and which was unfortunately destroyed during the Revolution, was built, and the sketches that are left to us show us its beauty and effectiveness secured through comparative simplicity. All the famous châteaux of France were either built or received their most famous additions under the influence of the new spirit that came into architecture under the influence of Francis I. Those of Bury and Blois and Amboise and Chenonceaux were products of this period. The staircase and the wing in the centre of which it stands at Blois are among the most admired, or at least the most frequently drawn, of the works of this age. All the other departments of architecture, besides the ecclesiastical and municipal, were affected by the enterprising spirit which entered into architecture at this time. Leonardo da Vinci offered to build fortifications under any and all circumstances, the more difficult the better, and succeeded in doing some excellent work. According to tradition he laid firm foundations, even under water, for certain French fortifications, and these still remain. In bridge building particularly this period did some excellent work. In the chapter on Social Work and Workers will be found an illustration of the bridge built across the Avon at Stratford by Sir Hugh Clopton about the time of the discovery of America, which shows that they could build beautifully as well as enduringly at this time. There are many private houses in the towns of Europe erected at this time, some of them even by families without any pretension to wealth or nobility, which illustrate very well how sincere and thorough was their domestic architecture, how beautiful because of its honest straightforwardness and how eminently enduring. Fra Giocondo, who edited the Aldine edition of Vitruvius in 1511 and who edited Caesar in 1513, introduced illustrations into these works, and particularly a plan of Caesar's bridge across the Rhine. He used his classical knowledge to good purpose, however, for in the service of the king of France he probably built two of the noble bridges that still span the Seine. These were finished early in the {132} sixteenth century. It would not be difficult to note other examples of this same kind in many parts of Europe at this time.