In the span of six hours on a recent Saturday, I cursed out one honking driver, leapt aboard three buses, rode seven trundling MBTA trains, posed for nine photos (including one with a lobster, one with a raven, and one with a dead Argentinean president), attempted to solve 12 riddles, made 14 cell-phone calls, traversed nearly 20 miles, recalled that the Great Molasses Flood claimed 21 victims, dodged at least 50 dawdling pedestrians, and yammered the phrase "30 green benches" more times than I care to remember.

This was all in the name of the Urban Challenge, a weekend event that’s touring 20 American cities over the course of 2002. The creation of Arizona attorney Kevin McCarthy, Urban Challenge is equal parts road race, scavenger hunt, and obstacle course. Teams of two aim to have their pictures snapped at 12 designated "checkpoints" — obscure locations throughout the host city that are only revealed in cryptic clue sheets handed out on game day. To reach these sites, competitors can travel only by foot or public transportation — no rollerblades, cars, or skateboards permitted. To decipher the locations of these checkpoints, players are encouraged to employ "any available resources," including cell phones, guidebooks, librarians, sympathetic strangers, and Internet-savvy allies at home who have nothing better to do on a weekend morning than perform countless Google searches. The fastest team to reach the 12 checkpoints — within the five-hour time limit — scores a free trip to Las Vegas and the opportunity to compete for $50,000 in the Urban Challenge finals.

Sounds easy, right?

In Boston, it wasn’t. I lost miserably. For my partner, I’d recruited a pal named Gavin, a former high-school track star who’s competed in everything from the James Joyce Ramble 10K to the Chicago Marathon. So along with two pens, a backpack, a compass, a cell phone, a voice recorder, a map demarcating Boston’s public-transportation routes, a cadre of hung-over friends willing to field queries, and a laminated Quick & Easy¨ map billing itself as "The Fastest Map in the East," Gavin and I set out with a sense of adventure, a sense of humor, and a willingness to fail.

And boy, did we fail.

8:05 a.m., the sidewalk in front of Atlas Bar & Grill, Lansdowne Street. By the looks of the 20-person procession snaking around Atlas’s concrete patio, today’s participants fall into two camps: runners and reality-TV rejects. The Bruce Jenner bloc is best represented by a sinewy man with spectacles strapped to the back of his head, a stern expression, and a heart monitor (geesh!), who’s simultaneously pinning a race number onto his partner and stretching out his hamstrings. Conversely, the wanna-be Amazing Race contestants look bleary-eyed and listless, despite being decked out in loud ensembles: YANKEES SUCK logos, a throng of matching sunburst-yellow shirts with raglan sleeves and tricorn hats, and a couple of Minutemen costumes. There’s even a pair of pale-skinned girls who’ve gone to the trouble of naming their team the "Cod Squad" and spangling their wide-brimmed bonnets with three-dimensional silver fish.

8:30 a.m., a table littered with dirty napkins inside the dimly lit Atlas Bar & Grill. The only sedentary segment of today’s "challenge" is a 30-question multiple-choice trivia blitz, complete with red-and-white bubble grids and number-two pencils. Since departure times are staggered over the course of a half-hour, these test results dictate each team’s start time.

The test is easy — more Anne Robinson than Alex Trebek. ("The name of the Brady dog was ... ?") Yet at this early hour, it feels like the bar exam. Still, either Gavin and I possess more combined knowledge than we realize, or everyone else here is abysmally stupid: we finish 11th out of 125 teams. This ranking ensures us a 24-minute head start over the lowest-scoring crews.

For a brief moment, I wonder if we have a shot. I start to get excited. Maybe this won’t be so difficult! Maybe we won’t fail miserably! Maybe we’ll win a free trip to Vegas! Maybe I’ll quit my job and become a full-time Urban Challenger!

9:06 a.m., Ipswich Street, a garbage-strewn side street near Fenway Park. Then I examine our first clue: Find a circular bronze plaque flanked by 30 green benches near water.

Me: "What? Huh?"

Gavin: "Okay, cell phone, cell phone."

Me: "I think that’s in the Common. Maybe even in the Public Garden."

Gavin (on the phone): "Hey there, we just took off, and we’re going to Checkpoint 1. We think we know. Ready for the clue? Find a circular bronze —"

Me: "It’s totally the Common."

Gavin: "We think it has to be in the Common."

Me: "It has to be. Where else would it be?"

9:28 a.m., Boston Common. Checkpoint 1 is not on the Common. It’s not in the Public Garden. And no one — not a local garbage collector, not an MBTA conductor introduced as omniscient, not even the personnel at the Visitor Information Center near the Common — can confirm the existence of a bronze monument and water adjacent to 30 green seats.

But everyone we speak to volunteers a guess. The Wharf. Jamaica Pond. Copley Square. The Hub of the Universe tablet. The reservoir near Cleveland Circle. The Esplanade. The Make Way for Ducklings sculptures.

As I soon discover, Boston pedestrians, either out of sympathy, pride, or abject fear, hesitate to admit their ignorance. Approach a middle-aged man meandering down the street and ask a question like, "Do you know where there are 20 stone sailboats in Boston?", and you’ll get an answer like this: "Ah, lemme see. Hmmm. I’m not sure. Hmmm ... " Such a response is a circuitous confession of ignorance, so it should be sufficient. But the spluttering never stops there. "Wait a sec. Twenty stone sailboats, you said? Hmm, that’s a tough one. I’ll be damned. I’ve lived in Boston for [insert an integer greater than five here] years, and that doesn’t ring a bell. But lemme see. Maybe if you try the Public Garden, you’ll find it."

(Twenty stone sailboats, by the way, are etched into a riverside boathouse.)