If you happen to be in Rio during the carnival, missing it is no option. Rio Carnival is a wild 5 days celebration, taking place every year 40 days before Easter from Friday to Tuesday. It usually happens in February, the hottest month in the Southern Hemisphere, when the Rio summer is at its peak. The typical Rio carnival parade is filled with revelers, floats and adornments from numerous samba schools which are located in Rio. The event is considered the biggest carnival in the world with two million people per day on the streets. It is not only the biggest Carnival, but also a benchmark against which every other carnival is compared and one of the most interesting & colourful artistic events on the Globe. If you miss the actual carnival, don´t worry. Carnival isn’t the only time to experience the spectacle and beat of Rio’s samba schools. As soon as Carnival finishes many of these schools will start rehearsals for the following year. Check out the Sambodromo rehearsal schedule here: http://www.rio-carnival.net/sambodromo/rehearsals.php These practice performances can be seen for free and will become more and more elaborate the closer it gets to Carnival, with full-dress rehearsals in the months just prior.
The main carnival events and rehearsals take place on the samba runway called the Sambodromo. They rehearsals at Sambodromo start in December. Subway station “Praça Onze” is 15 minutes walk from the Sambodromo. The subways run 24 hours a day during Carnival.
The ticket prices depend on day&place but basically you will pay around $100 for a sambodromo ticket. See the ticket prices from the below link to rio-carnival.net.