In 1198, on the election of Enrico Dandolo, the aristocracy carried their policy one step farther, and by the promissione ducale, or coronation oath, which every doge was required to swear, they acquired a powerful weapon for the suppression of all that remained of ancient ducal authority.
The promissione ducale was binding on the doge and his family, and could be, and frequently was, altered at each new election, a commission, Inquisitori sopra it doge def unto, being appointed to scrutinize the actions of the deceased doge and to add to the new oath whatever provisions they thought necessary to reduce the dogeship to the position of a mere figurehead in the state.
Above the Piazza della Signoria, at the highest point of the town, is the Palazzo Ducale, erected by the dukes of Urbino in 1474-1480; the architect was, in all probability, Lucio da Laurana, to whom is due the palace at Urbino, which this palace resembles, especially in its fine colonnaded court.
Opposite the Palazzo Ducale is the cathedral, dedicated to SS.
However this may be, the earliest positive evidence of the existence at Venice of a worker in glass would seem to be the mention of Petrus Flavianus, phiolarius, in the ducale of Vitale Falier in the year 1090.
Within the confines of the monastery is the Palazzo Ducale which since 1901 has been occupied by the Certosa museum.