Three months before the parade, dancers from different samba schools practice for the traditional parade in Rio de Janeiro late night at the Sambódromo. They're part of the first block to go in and they're called Comissão de Frente in Portuguese. It's a group of dancers that introduce the story of the year to the public. This part of the parade always brings surprises that can only be rehearsed late night far from the public's eyes and the competitors.
These secret rehearsals happen on the weekdays after work. The first dancers (in this story they represent Paraíso do Tuiuti Samba School), arrive around 10pm so they can all start around 11pm at the Sambódromo Marquês de Sapucaí, the official place for the Samba Parade. These rehearsals go until late at night.
Choreographers say the secret rehearsals are crucial to fit the presentation and test the traditional surprises within the space where the parade will take place. Usually, these rehearsals start in December but the official parade doesn't happen until February or March.