Revelers are celebrating Mardi Gras in New Orleans, Louisiana Tuesday 18 months after Hurricane Katrina devastated the city.

Crowds of people are decked out in purple, gold and green on floats as parades move through the streets of the city. In a tradition dating back centuries, tourists and locals alike try to catch beaded necklaces, painted coconuts and other souvenirs thrown from floats.

Not far from the party in the city's French Quarter, entire neighborhoods still lie in ruins after the storm, and almost 50 percent of New Orleans' population has not returned home.

Mardi Gras in New Orleans, also known as Fat Tuesday, is one of many celebrations around the world. There are similar Carnival celebrations in many parts of Europe and Latin America.

The largest Carnival celebration is in Rio de Janeiro, Brazil, which has been holding a four-day street party that ends Tuesday.

Carnival's origin lies in the Christian calendar. It is a time when people indulge in festivities before Lent, a six-week period of fasting and prayer that begins Wednesday.

Some information for this report provided by AP.