In 1516, the Jews of Venice were forced to move to an enclosed area, the site of an old metal foundry. The Italian word for foundry is "ghetto," thus giving rise to a byword that would, over the centuries, describe the persecution of Jews. In 1555, for example, Pope Paul IV created the Roman Ghetto, and in the 20th century the Nazis forced Jews into dozens of ghettos -- the Warsaw Ghetto alone held 450,000 people (30% of the entire population of Warsaw), crammed into a tiny area.