There are about 600 block parties in Rio during Carnival season. They usually kickoff with a marching band playing loud samba music. The blocos start in mid-January and become more frequent through Fat Tuesday. Some are highly organized and scheduled while others are spontaneous. Most are reserved for neighbors. A few attract thousands of revelers from across the city. There are also parties for special interest groups such as the handicapped. The biggest event is Cordão da Bola Preta on Saturdays. More than a million people attend the Black Ball from 9:00 a.m. until the wee hours the next morning. Collectively, all of these rambunctious celebrations are called the world’s largest party. During the last week or two of Carnival – when up to seven million people are having a great time – the street parties could also be called the world’s largest traffic jam.