The first architects—or _ingegneri_—were Filippo da Ancona and Giovanni da Milano. The latter was succeeded by Jacopo da Cortona in 1451. A year later the building was far enough advanced for the Castellan, Foschino degli Attendoli, to take possession. The day of his installation was of mystical import for the Duke, who chose a day approved by his astrologers, when the moon was waxing. Francesco, who desired to make his building beautiful as well as strong, engaged the Florentine architect Filarete to design and adorn a lofty entrance tower in the walls facing citywards. This tower, destroyed long ago by accident and time, is now represented by the modern Torre d’Umberto, in which it must be supposed that the architect has somewhat freely interpreted the scanty evidence in contemporary documents and drawings of the appearance of the original.[25] Footnote 25: A fifteenth century graphite drawing of Milan on a wall of the old monastery of Chiaravalle, a short distance from the city, shows the form of the castle at that time. The usual quarrels arose between Filarete and his Lombard fellow-architects, whom the Tuscan scorned as mere masons. Their jealousy and impatience defeated his ideas, and he was finally compelled to abandon the work entirely to them. The Duke’s decorative projects indeed came to little. His order to Jacopo da Cortona to make windows, _of such beauty of style and form as a work like this demands_, in the outer façade was never fulfilled, perhaps because of the inconvenience of such openings in a defensive curtain, and it was left to the restorer in these peaceful days to insert the Gothic windows—elaborately ornamented in imitation of some of the old ones still remaining in other parts of the building—which now adorn the front. After the first the work proceeded slowly, hindered by the quarrels of the architects, the irregularity of payments, and the dishonesty of those in charge. In 1454 the Duke’s military engineer, Bartolommeo Gadio of Cremona, was appointed to the chief post, which he held to the satisfaction of three successive despots till his death in 1484. Duke Francesco was destined never to inhabit himself this building which he had watched with such ceaseless interest, but when he died in 1466 it was complete in all its main features. Within the great walls which flanked Filarete’s tower and were guarded at the angles by two massive round towers lay the vast outer court, with fortified side gates, as well as the main entrance in the central tower. At the other end of this piazza rose a second mighty curtain of masonry, behind which lay the citadel, containing the Corte Ducale on the north side, and on the south a strongly defended inner enclosure, the Rochetta or innermost keep, the place of retreat in extremity. In this form we see the Castle to-day, though with all the defensive apparel which frowned from gates and tower and walls gone.