More than 2,500 people take part in each parade, which last about an hour, as groups of costumed participants and oversized floats make their way through the Sambodrome.
Each samba group is judged in 10 categories, from the quality of the drum sections to the beauty of costumes.
Whichever group comes in last is not allowed to compete in the next year's competition among the 12 best groups.
