Here's another way to see New York City: Run 100 miles through its streets.

That's what about 50 runners will attempt early Saturday morning when they take on the second annual Great New York 100 Mile Running Exposition, an under-the-radar endurance event that can take more than 24 hours to complete. One of the only urban 100-mile races in the country, the race featured only 14 finishers last year.

"It's a very small, low-key run, but it is gaining popularity by word of mouth," ultramarathoner Phil McCarthy, founder of the race, wrote in an email.

Staging the event is a feat in itself, requiring the coordination of volunteers to staff aid stations at far-flung points, not to mention the task of plotting 100 miles within the limits of New York City.

Runners will start in Times Square at 5 a.m. Saturday morning, heading northward through Central Park to the upper limits of the Bronx, eventually reaching the Rockaways and Coney Island, then across the Brooklyn Bridge to finish where they started. No roads will be closed. Amid so thin a field, onlookers likely won't realize a race is going on.

Most ultramarathons, defined as any race longer than the standard marathon distance of 26.2 miles, are hosted on trails or in the mountains. Runners often receive food, fluids and gear from friends positioned at designated points along the way.

What distinguishes this 100-mile event—which also features a 100-kilometer (62-mile) version—is it is entirely contained within an urban landscape, offering great city views while posing the tremendous physical challenge of pounding pavement for 100 miles.

That helps explain why barely half of last year's starting field of about 30 runners managed to finish.

"Your feet are what hurt the most. At mile 30 I needed to change my shoes," said Keila Merino, a 32-year-old New York City elementary schoolteacher who was the overall winner of last year's race.

Merino, who has completed more than 15 marathons and several 50-mile races, made last year's event her first 100-mile experience, which she finished on a 90-plus degree day in 21 hours, 5 minutes and 55 seconds.

At mile 90, she said, she knew there was only one runner ahead of her, so she began to focus on catching him. She completed the last mile of the race in a scorching 6:45, arriving in Times Square around 2 a.m. to the cheers of McCarthy, the organizer, and confused onlookers.

"They didn't know what was happening," she said.

This year, Merino will help pace her friend Chris Solarz, who finished last year's race in about 26 and a half hours. Solarz, 34, hopes to break her course record and dip under the 20-hour mark.

Success would give Solarz, who lives on the Upper East Side, two New York City distance records. In 2010, Solarz set a new Guinness world record for riding the entire subway system in the fastest time ever: 22 hours, 52 minutes, 36 seconds, slower than his hopes for Saturday's ultramarathon.

"You know, I really love New York City," Solarz said.

Write to Sara Germano at