Bay to Breakers: The rainbow-clad, costumed and sometimes naked 12K race that's both party and competition

It may be the only race on the planet that begins with the tossing of tortillas.

On Sunday, the Bay to Breakers road race takes place in San Francisco. According to race director Chris Holmes, it's like an unofficial holiday, and the only one that everyone in the city celebrates.

There are a group of about 10 to 20 people that dress up as salmon head-to-toe. And they run from the end of the race to the beginning of the race.- Phil Richardson, 2017 Bay to Breakers participant

Aside from the tortillas, the race is unique for its distance — it's 12K instead of the usual 21K for a half marathon. It's also unique for the runners and the crowd. Costumes, rainbows and nudity are all prominent alongside the serious runners who've also run the New York and Boston marathons.

It is a race with a party atmosphere, and as Holmes tells Day 6: "It's just an exciting and intoxicating thing to be a part of."

The history of the race

The race began in 1906 as a way to unite the city after San Francisco was devastated by an earthquake.

Over the years, Bay to Breakers has grown to include various unique traditions, including the tossing of the tortillas before the start of the race.

Thousands upon thousands of tortillas show up at the start line and are being thrown up in the air like giant confetti pieces.- Chris Holmes, Bay to Breakers race director

"I wish I could have a story as to where the tortilla throwing tradition began, but it has just taken on a life of its own," says Holmes. "Thousands upon thousands of tortillas show up at the start line and are being thrown up in the air like giant confetti pieces."

But the tortillas are just the start of the race-day fun.

Dressing up for B2B

"With a race that's over 100 years old, you could imagine there are a number of great traditions that come along with it," says Holmes. "One that we are most notably known for is the costumes that people wear."

People spend months working on their costumes for the race, whether organizing as groups or on their own.

Notable costumes from the past include a group dressed as a Jurassic Park-themed roller-coaster, a group dressed as a box of doughnuts, and of course there are always the Elvis impersonators.

Phil Richardson moved to San Francisco three years ago and competed in his first Bay to Breakers last year. He did so wearing a replica of Kellyanne Conway's inauguration day outfit.

"It was iconic. It hadn't been done, that I knew of. And boy, we had it custom made to where it was breathable and flexible enough to run in," explains Richardson. "I threw on a red hat, a blonde wig and some red gloves to go along with it and hit the trail."

Holmes says one of his all-time favourities is "a two-person Golden Gate Bridge costume, where both ends of the bridge were being carried by individuals the entire length of the racecourse."

"And this was a scale model of the bridge that was probably about eight feet in length. So it's not like the two people were right next to each other, and they somehow navigated the tens of thousands of people that are on the course."

And then there are the salmon.

"The one that everyone looks forward to every year are the salmon," says Richardson. "There are a group of about 10 to 20 people that dress up as salmon head-to-toe. And they run from the end of the race to the beginning of the race. So they run upstream and it's fun, it's comical, even the serious runners have to laugh and kind of just go around them."

Within the race there is also a category entitled "centipedes."

This is a category for groups of 13 or more who must be linked together, usually by a bungee cord, for the entire length of the race. This year marks the 40th year for centipedes in the race.

The atmosphere

The Bay to Breakers is a bucket-list race for many runners; it's an unusual distance that can provide change for runners, and it's a giant party.

"Approximately 40,000 people actually register for the race," says Richardson. "They're the ones that are at the starting lines. They're the ones throwing the tortillas."

"The people that run along the route are perhaps upwards of 100,000 people. People just jump over the sidelines in costume, or or naked, because of course they can't start to race naked. Or they just want to walk with their friends that they see participating," he says.

As race participants make their way up the Hayes Street Hill, past what Holmes calls the "Full House" Victorian homes, the race route becomes a giant party.

The homes along the route have house parties that spill out onto the road.

"You get to the top [of the hill], you turn around, and it is just a sea of humanity," says Richardson. "Parties going on on either side … music blaring, and 100,000 people running on the street. It's incredible. Something you are unlikely to see anywhere else in the world."

To hear more from Chris Holmes and Phil Richardson, download our podcast or click the 'Listen' button at the top of this page.