There is no single day of the week when "everything" is closed in Venice, as it is a major global tourist hub. However, Monday is the traditional day for many smaller, locally-owned shops and family-run trattorias to take a "riposo" (rest day), especially outside the main tourist areas. Most major museums and the Peggy Guggenheim Collection remain open on Mondays. The most significant closures occur on major public holidays: Christmas Day (Dec 25), New Year’s Day (Jan 1), and April 25, which is both Italy’s Liberation Day and the Feast of Saint Mark, the patron saint of Venice. On St. Mark's Day, you will find most local businesses closed, though restaurants in San Marco and Rialto usually stay open for tourists. If you want to experience Venice "at work," avoid visiting on Sunday or Monday, when the local artisan shops in Dorsoduro or San Polo are most likely to be shuttered.