In Venice, a huge number of all kinds of palaces, almost every house on the Grand Canal anyway fits this definition. The most important, of course, is the Doge's Palace (or Palazzo Ducale). The rest can be called a "palace" with a stretch, rather these are fanciful mansions.

Pay attention to Ca d'Oro, Ca 'Dario (Ca' Dario or Palazzo Dario), Palazzo Barbaro and Ca 'Rezzonico.
In Venice, you can even stop at night in some palace of the 15th century, for example, Palazzo Dandolo, which is now converted into a hotel.