NEW ORLEANS (Reuters) - New Orleans was transformed into one massive party on Sunday as the city prepared to host the 47th Super Bowl between the San Francisco 49ers and Baltimore Ravens.

San Francisco 49ers head coach Jim Harbaugh (L) greets his brother, Baltimore Ravens head coach John Harbaugh, during warm ups ahead of the NFL Super Bowl XLVII football game in New Orleans, Louisiana, February 3, 2013. REUTERS/Mike Segar

The city's French Quarter was packed with visiting fans soaking up the atmosphere before the biggest game in American professional sports was due to start at 6:30 ET (23:30 GMT).

Across the country, millions of people were having their own Super Bowl parties in preparation for a game that has all the ingredients of a classic.

The two teams left their hotels in the early afternoon and took a short bus ride through the crowded streets to the Superdome, which will be packed with more than 70,000 spectators.

For the first time in the 47 years of the Super Bowl, two brothers will go head-to-head for the National Football League championship.

John Harbaugh is Baltimore's head coach and his younger brother Jim has the same job with the 49ers and their sibling rivalry has dominated the build-up to the game.

The two players who have been the main focus in the lead-up to the game are Ravens linebacker Ray Lewis and San Francisco quarterback Colin Kaepernick.

Lewis is the only survivor from the Ravens team that won the Super Bowl 12 years ago. A 17-year-veteran of the NFL, who has spent his entire career with the Ravens, Lewis is retiring after the game.

Kaepernick's career is just starting. He began the season as San Francisco's backup quarterback but kept the job after getting his chance when Alex Smith suffered a midseason concussion.

While Lewis and the Ravens are chasing their second Super Bowl title, the Niners are attempting to win a sixth and tie the overall record held by the Pittsburgh Steelers.

The 49ers have never lost a Super Bowl, but this will be their first appearance in 18 years.

(Editing by Larry Fine)

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