officially it corresponds to four nights and three days, starting on the fat saturday's night and ending in ash wednesday's morning.  

however, many people in rio de janeiro tend to make the festivities start much earlier, with hundreds of block parties being held in the days prior, to capitalize on the popularity of carnival and the intense way the brazilians live it.

in the fat saturday's official opening of festivities, the mayor of rio gives the city's keys to king momo, the chosen king of the carnival, thus starting the official festivities.

the major events are the samba school parades held in the sambódromo of the marquês de sapucaí street, a structure built in downtown rio in 1984, specifically to host the parades of the most important samba schools.