The main entrance to the piazza dei Signori was to the south, beside the Duomo. The guard tower contained the precious clock, the first constructed in Italy, built by Jacopo Doni da Chioggia, doctor, astronomer and professor at the University of Padua. When the Venetians conquered the city in 1405 and began a project for reorganising the area, they favoured an orientation towards Piazza dei Signori. They demolished the main entrance at the palace, on the south, and also the Palazzo del Capitano with the secondary gate to the east. On the other side of the piazza they then built the sacristy for the Church of St. Clement, in a manner that it would serve as backdrop for the celebrations of the Serenissima. The new tower was built between 1425 and 1430, and on the 1437 Saint's Day the new clock was inaugurated, where still operates to this day. The clock was designed by Master Novello, orivolajo (clock-maker), and built by the Giovanni and Giampietro delle Caldiere, from Vicenza, on the model of the former clock by Dondi. It strikes the hours and indicates the days, months, and signs of the Zodiac. It does not include the sign for Libra, possibly because Master Novello followed Egyptian astrology, which included only 11 signs or, according to a legend, perhaps because the builders did not receive their payment. The triumphal arch was built under the supervision of Giovanni Maria Falconetto, in 1532.The tower was given a new appearance in the early 1500s, by Giovanni Maria Falconetto, who designed the base in the form a triumphal arch: an ample semicircular arch in Istria stone, supported on four twinned Doric columns rising from a high plinth, crowned by two Winged Victories and surmounted by an attic with the Lion of St. Mark.