SHORTLY BEFORE MY TREK through the Peruvian Andes, my friend Cassandra announced that the Inca empire’s cape-clad citizens are still floating around the ruins of Machu Picchu. “Actually,” she deadpanned, “they aren’t floating, but vibrating invisibly.” The possibility that I might encounter vibrating Incas gave me pause. I had always thought the Incas were killed off by the conquistadores midway through the sixteenth century, but Cassandra assured me they were still very much alive and had long ago reached a level of spiritual enlightenment so advanced that they could no longer be seen. “You’ll find them while hiking on the Inca Trail,” she told me with just a hint of a smile. “Or else, they’ll find you.”

By way of explanation, she gave me a copy of The Celestine Prophecy, which I read on the flight to Peru. (Three rows up, an older woman wearing enough silver loops in her left ear to hang a miniature shower curtain was also reading the book.) I had recognized the title from the New York Times best-seller list, where its more than three million readers have kept it for the past two years. The book’s simple prose makes The Bridges of Madison County look like something translated from Russian, but the spirituality it espouses—based on Ralph Waldo Emerson’s pantheism and a kind of ontological twelve-step program—is clever and catchy. And its final chapter echoes Cassandra’s assertion that the ancient Incas didn’t die out, but rather achieved the final transcendental “insight” and became, literally, a spiritual culture.

I spent two lazy days before my hike in the warm thin air of the ancient Inca capital of Cuzco (the Earth’s Navel, in the Quechua language), trying to acclimate my body to the 11,000-foot elevation in the endless chocolate-brown Andes, doing little more after exchanging my dollars for soles than drink coffee in the cafes surrounding the central Plaza de Armas and debate whether I should try the Andean delicacy of roasted guinea pig. The city has a colorful crafts market held every night under the arches around the plaza and a steady flow of young bohemian-looking backpackers with tanned faces, bloodshot eyes, and heady tales about their adventures on the trail. The locals are friendly, sometimes flirtatious, quick to make eye contact and smile. Many still wear traditional red-and-green wool ponchos and Bolivian bowlers. Occasionally an old woman will pass by with a shaggy llama in tow or a young boy will climb onto a rooftop to play his antaras, the Andean Pan pipes made from bamboo. With the rusty Spanish learned during my undergraduate days in the early eighties at the University of Texas at Austin, I managed several halting but enjoyable conversations with Peruvian soldiers, shopkeepers, and clusters of uniformed schoolchildren, all of whom wanted to know about Texas and if I was planning to hike the Inca Trail to Machu Picchu (Old Peak), the famous Lost City of the Incas.

A number of tour agencies with offices on the Plaza de Armas offer porters and guides for river-running tours down the Urubamba or for the twenty-mile hike through the Andes to the Lost City, which poet Pablo Neruda called “Mother of stone and sperm of condors.” Although I was a little nervous about thieves, the altitude (the first pass on the trail reaches a height of almost 14,000 feet), the cold nights (after the sun sets, temperatures often plummet below freezing), giardia, broken bones, getting lost, and general loneliness, I resolved on the eve of my departure to venture to Machu Picchu on my own.

Saturday morning, well before sunrise—with roosters crowing in the hills—I boarded the local train from Cuzco to the Km 88 station, a beautiful but bruising three-hour ride over the mountains to the official start of the Inca Trail. I was unnerved a bit by the fact that I was the only person getting off the train at Km 88 (presumably everyone else was riding to Machu Picchu), but I quickly focused on the task at hand. Boots tightened, baseball cap donned, forty-pound backpack secured, I crossed high above the white water of the Urubamba on a swaying suspension bridge, paid the $14 trail fee (which included entry to Machu Picchu), registered with the trail guards, checked my map and compass, and headed east through a eucalyptus grove, past a small Inca ruin called Llactapata (Town on Hillside). Because of the heat—by midafternoon it was pushing 90 degrees—and the steep ascent of the rocky trail, it was difficult to appreciate the beauty of the surrounding countryside, which included one or two small farming villages with terraced crops and a tremendous view of the 19,000-foot snowcapped Veronica Mountain. The trail followed the Cusichaca River for several miles before turning west into much more isolated territory. The warm breeze kicked up dust and the smell of long-gone packhorses. Condors circled overhead. I pitched my tent an hour before dark at a fork in the smaller Llullucha River, boiled some river water for soup, and was soon flat on my back under a tree, exhausted, sunburned, scribbling a few lines in my journal by flashlight.

I don’t know if it was because of the altitude or my profound weariness, but as soon as I turned off the light and stared up through the branches at the star-filled sky, something spooky occurred. Alone at night, out in the empty mountains, I gradually, almost eerily, began to feel with my skin and breathing that mysterious thing within the tree that causes its limbs and leaves to reach for the sun—the tree’s soul, or life force, or whatever it is that with the tree’s death goes elsewhere. Although the sensation was weird, it was pleasant: I felt that I was not alone. Perhaps the experience was less a result of some rarefied spiritual communion than a by-product of reading The Celestine Prophecy. Either way, it made sleeping by myself in the mountains that first night much easier.

Midway through the second morning on the trail, I met up with Noa and Nurit, two lovely raven-haired sisters in their early twenties who had come to Peru after completing a stint in the Israeli army. They were accompanied by two sweating Peruvian porters hired in anticipation of the trek’s most difficult climb: Abra de Huarmihuañusca (Dead Woman’s Pass). We decided to tackle the cloud-covered 14,000-foot pass together, encouraging and occasionally pushing each other. (To give you a sense of the altitude, the Denver Broncos’ Mile High Stadium, where visiting teams often use oxygen tanks on the sidelines, is perched at around 5,300 feet.) The climb took an agonizing three hours; with each step a membrane seemed to thicken over our lungs and brains, but if we lost focus even for a moment, we could have tumbled off the narrow trail into oblivion. At one point—with my head throbbing and my heart pushing itself into unkown territory—I stopped and fumbled through my backpack, searching unsuccessfully for the bottle of aspirin I could have sworn I had brought. Seeing my distress, one of the porters offered me a handful of native coca leaves (legal in Peru, he assured me). As I chewed them, my load seemed to lighten by ten or fifteen pounds.

After a brief rest at the top of the pass, we said good-bye to the porters and watched them disappear mysteriously into the cloud forest. Noa and Nurit strapped on their backpacks and continued with me down the valley toward the Pacamayo River. The descending trail was easier on our shoulders but significantly tougher on our knees. As we broke back through the layer of clouds, we inhaled with pleasure the earthy smell of the river marsh and glimpsed dozens of tiny blue Andean hummingbirds fluttering over the damp, knee-high grass. (More than once we cocked our heads at what sounded like ghostly flute playing.) In the distance we could see the Runturacay ruin, an egg-shaped Inca lookout hut that seemed to cling precariously to the side of the next summit. With dusk approaching and almost eight hours of hiking under our belts, we decided to pitch our tents by a small waterfall near the river, saving the next two passes for the following day. Even after a two-hour descent, we were still almost 12,000 feet above sea level. Giddy from the altitude, our exhaustion, and a sense of accomplishment, the three of us fixed pasta and tea for dinner and chatted around our little campfire as the sun dipped behind the surrounding peaks.

We awoke on the third day of the trek an hour before dawn. Because of our stiff muscles, the early-morning air felt painfully cold and damp. After finding ice on my tent, I reached into my backpack for my new high-tech polypropylene parka, which I’d worn the previous evening, only to discover that it was gone. Puzzled but too cold to fret over the coat’s strange disappearance, I accepted from Noa a handmade alpaca sweater—a traditional Peruvian pullover that she had bought back in Cuzco’s outdoor market—and broke camp feeling surprisingly warm and refreshed.

At midmorning we were passed near the Runturacay ruin by a large, grunting, red-faced British tour group trailed by almost two dozen porters carrying everything from folding tables to a portable camp toilet. A thousand feet below us in the second valley, the undulating line of porters and Brits (all of whom trudged along with shiny red ski poles) looked a bit like a slow-moving caterpillar. Noa, Nurit, and I didn’t cross paths with another human for hours, meaning we had to ourselves the wonderfully scenic mountain landscape, including a couple of small algae-covered lakes and the two most interesting Inca ruins so far on the trail: Sayacmarca (Dominant Town), with its breathtaking granite staircase, and Phuyupatamarca (Town Above the Clouds), with its ritual baths and grand view of the last valley before Machu Picchu. This stretch of the trail descended dramatically downhill (at points only two feet wide, with a drop of several hundred feet) and comprised a mind-boggling succession of enormous stone steps. Gradually I came to realize what an enormous feat the Incas had pulled off, and I scratched my head, wondering how on earth they did it.

Noa, Nurit, and I spent the night on the jungly trail near the hillside Inca site of Huiñay Huayna (To Plant the Earth, Young). Surrounded by yellow orchids, low-hanging clouds, and a handful of Italian and Swiss backpackers also preparing for the last leg of the twenty-mile journey, we double-checked our map and then settled around our campfire, drinking tea and gazing up at the stars in a contemplative silence before drifting off to our tents.

Just three hours into our last day on the trail, after a series of dark tunnels, primitive wooden bridges, and the gentle explosion of hundreds of velvety black butterflies, we reached Intipunku (Sun Gate), the ruin at the top of the final mountain overlooking the colossal Huayna Picchu (Young Peak). Deep in the valley below was the culmination of our challenging hike: Machu Picchu. None of us said a word. Snapping a photograph seemed a futile way of capturing the splendor, so we simply took deep breaths and stood on the high pass for many minutes, hands clasped on our heads, trying to fully absorb what must surely be one of the most spectacular visions in all the world.

After we descended from the Sun Gate on the Inca Trail’s final stone-tiered segment, we checked our backpacks with a guard at the Lost City’s formal entrance and then roamed around the ruins all afternoon, tagging along with several tour groups as they learned in their guide’s Quechua-accented French or English about the Royal Tomb, the Temple of the Three Windows, the Sacristy, the Sacred Plaza, and the House of the High Priest. We were mystified by every aspect of Machu Picchu, from the sixteen dazzling ceremonial baths to the stone altar and Serpent Window of the Temple of the Sun. Why did the Incas build a city out in the middle of nowhere, entirely surrounded by mountains? How could they transport the enormous stones without modern machinery? Why did they leave, and where did they go? Touching the Condor Temple, which has a window that is perfectly aligned with the winter solstice sunrise, or the Hitching Post of the Sun, an elegant stone column used to predict the passing seasons, you would swear that the stone is still warm from the Incas’ tools. It’s clear that the Incas approached their magical masonry with reverence for the natural world and an awe-inspiring—perhaps divine—talent. No wonder so many experienced world travelers, people who have beheld the Taj Mahal and the Great Wall of China, often agree that nothing in their journeys quite compares with the haunting majesty of Machu Picchu. Seeing the Lost City with your own eyes in some strange way changes you into a slightly different person.

Completely exhausted from our adventure up to and through the ruins, Noa, Nurit, and I finished off the last of our food and water in the shade from the Hut of the Caretaker, exchanged addresses and final hugs, and then bid farewell as we went our separate ways. Knowing I might never return, I gave Machu Picchu a last look over my shoulder, headed down the winding four-mile road to the train station in the Urubamba Valley, and trudged eastward along the railroad tracks to the tiny village of Aguas Calientes. I showered, shaved, and rested my weary bones in a warm bed at Gringo Bill’s, and when I awoke the next morning, I took an hourlong soak in the natural thermal springs in the hills north of town.

Before catching the train to Cuzco and starting my long trip back to America, I shared several lukewarm Cusqueña beers with a local woman named Nydia, the representante ejecutiva of the lone tour agency in Aguas Calientes that offers three-day “spiritual visits” to Machu Picchu. Her take on the Inca mystery was succinct and oddly familiar: The city’s 30,000-pound stones were lifted and arranged using “spiritual vibration,” and the structures were vacated after a bolt of lightning struck the Temple of the Sun—a “definite bad omen,” she explained. She declined my offer to pay for her beers but suggested that we make a swap in the name of “intercontinental harmony”: my baseball cap for her old Peruvian wool beanie and the tiny flute (called a piruru) hidden under her capelike serape.

Two days later Cassandra greeted me at the Austin airport. I was seven or eight pounds lighter than the last time she saw me, tanned from the Inca sun, and wearing my new handmade Andean sweater and wool cap; I carried in my pockets the piruru, one or two soles, and the remains of several crumbled coca leaves. “Great trip, but I’m not sure I got it,” I said, returning with a shrug her dusty green copy of The Celestine Prophecy.

She pointed to my Peruvian attire and gave a knowing smile. “No,” she replied, tugging on my baggy jeans, “they got you. Look—you’re beginning to disappear.”

Travel Details The best time to hike the Inca Trail is during the Andes’ drier season, roughly May to September. A round-trip ticket from Austin, Houston, or Dallas to Lima costs about $900; flexible travelers without hotel reservations should have little trouble finding a place to stay in Cuzco for $2 to $50 a night. Peter Frost’s Exploring Cuzco and Lonely Planet’s travel book on Peru are both excellent guides for trekkers.

Freelance writer Keith Kachtick lives in New York City.