300 Manhattan Climbing Routes, and Not One of Them Indoors A long, thin crack runs up a craggy gray slab of rock outcrop overlooking the Hudson River in Fort Tryon Park. Few pay it much attention. Runners jog past. Dogs trot by, occasionally raising a leg. Couples cuddle on a bench nearby. For Gareth Leah, however, this is a piece of his urban Yosemite, an opportunity for an outdoor pursuit resting in rare New York anonymity. Standing a few feet from the rock face, he contemplated it for a second, like a boxer sizing up his opponent, then sprang into action: his left big toe crammed into the crack, his index finger hooked around a small dimple. Then he pulled. Four moves later, he was standing atop the 12-foot-high boulder, dusting excess chalk off his hands. "I was so amazed when I was talking to people and they'd say, "I'd love to go climbing but I don't know where to go,"" Mr. Leah said as he scampered down one side of the rock face. After hearing that lament countless times, he said, "it kind of started some slight ideas in my mind." And so Mr. Leah has spent over a year examining jug holds, cracks, toe holds and slabs to write "NYC Bouldering," a guidebook detailing over 300 bouldering routes that traverse rock faces throughout Manhattan. The book will be published in August by Sharp End Books. The sport of bouldering, which involves short climbs, usually with no ropes or harnesses, is not new to New York, which is home to several world-class indoor venues. But the idea of climbing actual outdoor rocks, tucked away in parks and along highways amid towering skyscrapers, remains relatively obscure within the city's climbing community, which is primarily centered on a few select boulders in Central Park. Mr. Leah first encountered outdoor rock climbing in Manhattan at Rat Rock, a craggy, chalk-dusted outcrop shaped like a lumpy potato. The name of the spot, in the southwestern section of Central Park, derives from the many rats and crack vials that littered the top before climbers gradually made the spot their own. "Back in the "80s, there was only about 15 of us," said William Piehl, a personal trainer who has been climbing around New York City for over 25 years. Then other people started to come in and we got a name, and everyone would go right to Rat Rock. There was never really a guidebook for it. It was a lot of word-of-mouth to get to other spots. The city may be covered in asphalt, concrete and steel, but long before it was settled, Manhattan was a raw island of mostly glaciated schist rock. So, as Mr. Leah set about documenting Manhattan's climbing rocks, he used a tool often found in the hands of climbers but rarely in other New Yorkers": topographical maps. "There are fault lines that run all the way through Manhattan," Mr. Leah said. I found that if you follow the fault line, you can find rock pretty much everywhere. So, I spent two months just walking up and down the fault line mapping where all the rock was in the city. His explorations yielded discoveries of rock faces as diverse as the city they sit in. Bouldering routes, often referred to as "problems" or "projects," are graded on a scale of v.0 to v.15, depending on their degree of difficulty, with v.0 being the easiest. Mr. Leah, with help from his book's photographer, François Lebeau, who is also a climber, and Mr. Piehl, found projects as easy as v.0 and as difficult as v.14. Other projects, including one on a tall, Easter Island-esque boulder on the south slope of Fort Tryon, have not even been successfully climbed. As Mr. Leah finds new routes to climb from Chelsea to Inwood, indoor gyms around the city continue to multiply. Brooklyn Boulders, an enormous rock climbing gym in Gowanus, Brooklyn, is considering adding a location in Queens. In Long Island City, the Cliffs is scheduled to open this summer with over 30,000 square feet of climbing space, making it one of the largest climbing gyms in the country. The gyms are also helping to send more climbers outside, according to Lorenzo Montañez, a Bronx native who has been climbing around New York for about a decade. He credits Mr. Leah for finding "so many new lines in rocks that I never gave much thought to," and is hoping the guidebook will help augment the outdoor climbing scene. "I can actually walk around with a crash pad and people would know exactly what it is that I'm carrying around," Mr. Montañez said, referring to the three-inch-thick foam pads to cushion falls often carted around on a climber's back like a turtle shell. "They'd say, "Oh, you're going to go climbing, dude? Can I see, or come along? Because I climb, too."" Below is an excerpt from Mr. Leah's guidebook, with 10 bouldering problems for Rat Rock. Click here to download. NYC Bouldering Guide Excerpt - Rat Rock (PDF) NYC Bouldering Guide Excerpt - Rat Rock (Text)