The "greatest free show on Earth" is not a one-day celebration. It's not even a one-week celebration. It is a month-long amalgam of parades and balls leading up to the season of Lent. In New Orleans, Mardi Gras proper, or Fat Tuesday, is the biggest day that attracts most locals and tourists. It falls on Feb. 25 this year and will feature parades hosted by some of the largest and oldest krewes, such as Zulu and Rex.