When, in the seventeenth century, painting had declined south of the Alps, Dutch and Flemish masters,--above all, Rubens and Rembrandt,--developed a new and admirable school of painting. To Van Dyck, another Flemish master, we owe many noble portraits of historically important persons.[244] Spain gave to the world in the seventeenth century a painter whom some would rank higher than even the greatest artists of Italy, namely, Velasquez (1599-1660). His genius, like that of Van Dyck, is especially conspicuous in his marvellous portraits. [Illustration: GIOTTO'S MADONNA] [Illustration: HOLY FAMILY BY ANDREA DEL SARTO] [Sidenote: Geographical knowledge in the Middle Ages.] [Sidenote: Marco Polo.] 127. Shortly after the invention of printing, which promised so much for the diffusion of knowledge, the horizon of western Europe was further enlarged by a series of remarkable sea voyages which led to the exploration of the whole globe. The Greeks and Romans knew little about the world beyond southern Europe, northern Africa, and western Asia; and much that they knew was forgotten during the Middle Ages. The Crusades took many Europeans as far east as Egypt and Syria. As early as Dante's time two Venetian merchants, the Polo brothers, visited China and were kindly received at Pekin by the emperor of the Mongols. On a second journey they were accompanied by Marco Polo, the son of one of the brothers. When they got safely back to Venice in 1295, after a journey of twenty years, Marco gave an account of his experiences which filled his readers with wonder. Nothing stimulated the interest of the West more than his fabulous description of the golden island of Zipangu (Japan) and of the spice markets of the Moluccas and Ceylon.[245] [Sidenote: The discoveries of the Portuguese in the fourteenth and fifteenth centuries.] About the year 1318 Venice and Genoa opened up direct communication by sea with the towns of the Netherlands.[246] Their fleets, which touched at the port of Lisbon, aroused the commercial enterprise of the Portuguese, who soon began to undertake extended maritime expeditions. By the middle of the fourteenth century they had discovered the Canary Islands, Madeira, and the Azores. Before this time no one had ventured along the coast of Africa beyond the arid region of Sahara. The country was forbidding, there were no ports, and mariners were, moreover, hindered in their progress by the general belief that the torrid region was uninhabitable. In 1445, however, some adventurous sailors came within sight of a headland beyond the desert and, struck by its luxuriant growth of tropical trees, they called it Cape Verde (the green cape). Its discovery put an end once for all to the idea that there were only parched deserts to the south.