Carnival is Rio's main event. It happens at the peak of summer, when Cariocas are at their best. Festivities attract thousands of people from all corners of the world. Carnaval, as spelled in Portuguese, is a 4-day celebration. It starts on Saturday, and ends on Fat Tuesday, or Mardi-Gras. Carnival Sunday is seven weeks before Easter Sunday. Dates change every year, in 2008 it happened from February 2 through 5.
The origins of Carnival are unclear, but most agree that it started as a pagan celebration in ancient Rome or Greece. Carnival balls were imported to Rio from Italy in the late nineteenth century, and had their golden era in the 1930 through 50's, with legendary balls at the Copacabana Palace and the Municipal Theater.

The Samba Parade began in the 30's - first timidly at Praça Onze, and later on Av. Presidente Vargas. It found a permanent home in 1984 at the Sambadrome a structure in the downtown area. Today Samba Parade is broadcast to dozens of countries, and all Brazilian states. Many people think of it as the greatest show on earth.

Carnival: http://liesa.globo.com/