Rio de Janeiro's Carnival parade is world famous for the samba dancing, costumes that leave little to the imagination and the magnificent floats that roll down Avenida Marques de Sapucai, also known as the "sambadrome". For the competitors, getting to the big show is months in the making.
Here are questions and answers about what goes into the big show that is Carnival:
HOW DOES IT WORK?
Competing schools of samba spend much of the year preparing for a 75-minute presentation that must include at least six floats to tell a story in an innovative way - while participants dance and sing, of course. The competitions begin on Sunday night (local time) and goes into Tuesday morning.
The winners get a trophy, national bragging rights for a year and a party on Ash Wednesday. Samba schools that fail to place high are relegated to a second-tier league the following year.
Carnival parades are such a serious business in Rio that one university even has a graduation program for samba school managers.
HOW DID THE PARADES COME ABOUT?
In the second half of the 19th century, posh clubs of Rio organised Carnival parties. Little by little, these gatherings gave up the elegant ballrooms and took to the streets. The poor also had their parties far from the city's elite south zone. Costumes were often used to satirise politicians.
As the 20th century began, many of these celebrations included "confetti wars" in which groups would throw paper decorations in the air and at each other. Still, they were non-moving events that featured wind instruments and horns, not the drums and dancing of today.
The first samba school appeared in 1928 downtown Rio. The concept behind "Deixa Falar" (Let them Speak) was to parade to the sound of samba, and it was a hit. In 1932, journalist Mario Filho organised the first competition of samba schools. A tradition was born that would inspire cities across Brazil.
WHO MAKES UP THE SCHOOLS?
Each of the samba schools of Rio represents a specific region of the city, often a favela. However, particular schools usually have fans all over Rio and even some nationally.
Up to 4000 members can take part in the parade of each of the 12 top-flight samba schools in Rio. The heart of the samba school is the drums section, with at least 200 people. As a form of reverence, the oldest members bring up the rear of an ensemble.
Up to 80,000 people watch the parades at Rio's sambadrome on Sunday night, all Monday and into Tuesday morning. Millions more watch on television. Tourists are allowed to participate in samba schools, but their costumes usually cost more than those for locals.
HOW DOES JUDGING WORK?
Rio's samba school league picks 54 judges who spread out across the sambadrome. There are six judges for each of nine criteria, including drums section, costumes and samba dancing.
Hours before the first parade, a lottery chooses four judges for each category. They will have their scores counted. The other two judges will only be counted if one of the other four is absent during the parade. The group that gets the best scores wins.
Sometimes winners and runner-ups are separated by 0.1 points. There were also several occasions in which two or three have tied as winners.
WHO SHOULD YOU KEEP AN EYE ON?
The green- and rose-colored Mangueira group often draws the biggest crowds at the sambadrome and fans across Brazil. They have won the parade 19 times, including last year's.
Blue and white Portela is historically the biggest winner, with 21 titles. Both Portela and Mangueira are home to some of Brazil's most popular samba artists.
The red- and white-colored Salgueiro is seen as the most popular among celebrities. It has won the parade nine times and it often has the most popular samba songs that fans in the sambadrome sing along to.
WHO PAYS FOR IT?
Rio's city hall is investing 24 million Brazilian reals this year (about A$10.4 million). The rest comes from sponsors, sambadrome ticket sales, samba school parties throughout the year that raise funds and a group of shady gambling businessmen called "bicheiros."
"Bicheiros" run a widely popular but illegal gambling game called "jogo do bicho," or "animal game" in Portuguese. They are sometimes linked to criminal organizations, and many sponsor local samba schools to improve their image.
WHAT WAS THIS YEAR'S CONTROVERSY?
After a day in silence, Rio's evangelical Mayor Marcelo Crivella delayed the traditionally opulent starting ceremony until 8.30pm. Friday only to skip it with the excuse that his wife was sick. Rio city hall eventually put out an email saying that Carnival was "officially open".
Revellers had been waiting hours at the sambadrome for the traditional handing over of the city's key to "Rei Momo", or the king of carnal delights. This has been always done with great fanfare in the past. But Crivella sent the head of Rio's tourism agency to do the honours. Rei Momo did not give interviews as usual and instead was quickly escorted out of the sambadrome by security guards.
It isn't clear whether Crivella, a retired Pentecostal bishop who took office on January 1, will attend any of the five days of parades at the sambadrome. Rio's city council has already authorised him to travel abroad on the next few days, but he has not announced where he might go.