One of the city’s contributions to the English language is the old Venetian word “ghetto.” Thousands of Jews regarded Venice as a sanctuary in the 14th century, after being expelled from the rest of Europe. The small area in Cannaregio is still set apart from the rest of the city, and these days has a poignant air about it. The ghetto needed no walls: Christian guards patrolled at night on canal boats, ensuring that no one crossed any bridge after curfew. Today just 450 Jews remain in Venice, and the five synagogues, dating to the 16th century, feature heavily carved interiors, though in a fragile state. The ghetto’s guides open the buildings only during tours, which they run several times a day.