One hundred years ago this month, a young lecturer in history at Yale University named Hiram Bingham made what at the time was celebrated as an historic, indeed heroic, climb through the Peruvian Andes at the climax of which, as Mark Adams puts it in this entirely delightful book, “he stumbled across the geometric splendor of Machu Picchu.” Honored at the time as one of the greatest explorers of the day — it was the day, mind you, of Peary and Scott and Amundsen — he has since lost a good deal of his luster, in part because Machu Picchu had been known for years to many Peruvians before his “discovery” and in part because of Yale’s adamant refusal until late last year to return to Peru the hundreds of antiquities he carried away.

It occurred to Adams, a magazine editor in New York, that “the revised version of Bingham’s tale had the makings of a great story: hero adventurer exposed as villainous fraud.” Poring over Bingham’s voluminous papers at Yale, he realized that Bingham was a considerably more complex (and interesting) figure than “the revised version” had suggested and that he wanted to go to Peru and retrace Bingham’s steps: “Bingham’s search had been a geographic detective story, one that began as a hunt for the Lost City of the Incas but grew into an all-consuming attempt to solve the mystery of why such a spectacular granite city had been built in such a spellbinding location: high on a secluded mountain ridge, in the misty subtropical zone where the Andes meet the Amazon. Fifty years after Bingham’s death, the case had been reopened. And the clues were still out there to be examined by anyone with strong legs and a large block of vacation time.”

So Adams went to Peru and connected with John Leivers, an Australian in his 50s “who’d been recommended . . . as one of the best guides in South America.” As Adams doubtless would be the first to admit, he couldn’t have undertaken the project without an experienced guide. Though he was married to a Peruvian and had visited Lima often, he “had never hunted or fished, didn’t own a mountain bike and couldn’t start a fire without matches if ordered to do so at gunpoint.” His self-portrait is refreshingly candid:

“Have you ever seen Mr. Travel Guy? He’s the fellow who strides through international airports dressed like he’s flying off to hunt wildebeests — shirt with dozens of pockets, drip-dry pants that zip off into shorts, floppy hat with a cord pulled tight under the chin in case a twister blows through the baggage claim area. All of this describes exactly what I was wearing. Between my microfiber bwana costume and the bags of candy that [a Peruvian] kept foisting on me, I could have been trick-or-treating as Hemingway.”

He was game, though, so he set off from Cusco with Leivers, accompanied as well by a legendary Peruvian mule driver, a diminutive cook, a half-dozen mules and a couple of guys to drive them. As outlined by Leivers over breakfast, the trek looked manageable: “About a hundred miles of walking, by my rough calculations. From the sound of what John had described, we’d go north, cut through the mountains, bear left toward the jungle, then double back toward Cusco. For the big finish, all we had to do was follow the river and turn right at Machu Picchu. This last part sounded like a pleasant afternoon stroll, something to kill a few hours and work up an appetite for dinner.”

‘Turn Right at Machu Picchu: Rediscovering the Lost City One Step at a Time’ by Mark Adams. Dutton. 333 pp. $26.95 (Dutton)

It turned out, needless to say, to be considerably more challenging than that, both because of the physical rigors entailed in walking — hiking and climbing were more like it — through some of the world’s most beautiful but rugged terrain, and because, like countless others before him, Adams was trying to unravel the incredibly complex tangle that is Inca history. “Separating fact from fiction in Inca history is impossible,” he writes, “because virtually all the sources available are Spanish accounts of stories that had already been vetted by the Inca emperors to highlight their own heroic roles. Imagine a history of modern Iraq, written by Dick Cheney and based on authorized biographies of Saddam Hussein published in Arabic, and you’ll get some idea of the problem historians face.”

Not merely is Inca history difficult to pin down, but Machu Picchu itself is an enduring mystery. “No one could say with confidence exactly why this extraordinary complex of stone buildings had been constructed in the first place,” Adams writes. “Was it a fortress? A sun temple? A really elaborate granary? A spiritual portal to the fourth dimension, constructed by extraterrestrial stonemasons?” Only Bingham — organized and self-confident to the nth degree — was confident he had the answer: he “was certain that he’d found the legendary Vilcabamba, famous as the Lost City of the Incas,” a theory that is dismissed by “modern Machu Picchu experts” as “ridiculous.”

Leivers had his own theory. He “believed that Inca sites like Choquequirao and Machu Picchu weren’t so much separate entities as parts of a vast Inca network,” like “organs and vessels, the circulatory system in a . . . very big living body” that covered “thousands of square miles.” Others believe that it was built as the tomb of the great Inca emperor Pachacutec, or as (in the recent words of two scholars) “merely one of [a] number of personal royal estates built by an Inca king in the remote countryside,” or as, in combination with the Inca Trail, a “pilgrimage route.” Adams gives all of these theories their moment, but finally concludes that “Machu Picchu is always going to be something of a mystery. Which is, of course, part of its allure.”

En route to this judgment Adams makes his way to a number of extraordinary places, all of them spectacular but pale by comparison with Machu Picchu. He has a few adventures and a scare or two, and gets a considerably deeper immersion in Peruvian life and culture than he’d previously been exposed to in Lima. “Peru is a wonderful place,” he writes. “It is also wonderfully weird.” He cites the strange behavior of its criminals, some of whom have held high elective office, and finally decides: “It’s possible that all this craziness is just geography as destiny. Peru’s borders contain some of the world’s most varied topography and climate. Measured in square miles, the country is not especially large. On a globe it looks like a swollen California. Within that space, though, are twenty-thousand-foot peaks, the world’s deepest canyon (twice as deep as the Grand Canyon), unmapped Amazon jungle and the driest desert on earth. . . . Scientists have calculated that there are thirty-four types of climatic zones on the face of the earth. Peru has twenty of them.”

Peru also has “la hora peruana, Peruvian Time.” Anyone who has ever made an appointment with a Peruvian plumber or delivery service knows all about it: “This is the code, indecipherable to North Americans, by which Peruvians determine the latest possible moment that it is acceptable to arrive for an appointment. The statement ‘I’ll be right back’ can mean just that, or it can mean that the speaker is about to depart via steamship for Cairo. . . . By one estimate, each Peruvian arrives a total of 107 hours late each year, a number that is shocking only because it seems so low. My friend Esteban, an Ivy League-trained businessman living in Lima, needed to lie to his mother in order to get her to his wedding on time. He told her the ceremony began at noon when it actually started at 4 p.m. She arrived at ten minutes to four, red-faced and puffing.”

Jonathan Yardley is the author of the newly published “Second Readings: Notable and Neglected Books Revisited.” The contents first ran as a series of essays in The Washington Post.