The expedition in Thanh Hoa was a success, and my book was published the following year. It got a good review in The New York Times, which seemed like the most important thing in the world at the time. Yet in retrospect the most significant event of the trip came at the end, on the eve of our departure from Hanoi. Russ Ciochon and I were wandering through the Old Quarter and came upon a trim bamboo house flying the flag of the People’s Republic of Kampuchea, the puppet government installed by the Vietnamese after they invaded Cambodia in 1979, ending the disastrous, bloody regime of the Khmer Rouge. We were greeted by a remarkably cheerful man named Bun Sambo, who appeared to be the only person there. He made tea for us, the necessary preliminary to any conversation, and then asked what he could do for us. It was an easy question. I replied, “We want to go to Angkor.”

When we first met, Ciochon and I bonded over our shared lifelong passion for the ruins of Angkor in central Cambodia, the classic model of a lost city in the jungle. We had collected nearly identical Angkor libraries, starting with the April 1960 issue of National Geographic, which featured the article “Angkor, Jewel of the Jungle,” by W. Robert Moore. The story was accompanied by a series of lurid paintings, alternately sexy and gory, that depicted life in Angkor at the zenith of the Khmer Empire. Ciochon and I had both read the old French archaeological studies and a madly overwritten memoir of an Angkor pilgrimage by the French travel writer Pierre Loti. Loti’s rapturous descriptions of the ruins promised an experience that fell somewhere between a religious vision and an orgasm.

Mr. Bun smiled and said, “You want to go to Angkor? I can arrange that for you.”

And so he did. Six months later, Ciochon and I flew to Siem Reap, the town near the ruins, and checked into the Grand Hotel d’Angkor. In its decaying art deco magnificence, the hotel looked like an exile from the Riviera, condemned to molder in the jungle. The lobby ceiling soared twenty feet overhead, making the sagging rattan furniture look dwarfish. The room reeked of the signature fragrance of the tropics, a heady mélange of mildew, fermented fish paste, and bug spray. Spiders had colonized a Parisian-style cage elevator, a former marvel of modernity that hadn’t ascended in decades. After we checked in, Ciochon, sick with the usual complaint, ran to the room. I sent up four bottles of cold lemonade and returned to the waiting car.

I had promised Ciochon that I would save Angkor Wat, the largest and most famous temple, for him and told the driver to take me to Angkor Thom. The capital of the ancient empire, Angkor Thom occupies six square miles of cleared tropical forest, crowded with ornately carved stone temples and palaces. When the French naturalist Henri Mouhot came here in 1860, he found the place completely overgrown by jungle vegetation. In a burst of enthusiasm, he declared that the ruins of Angkor were “grander than anything left to us by Greece or Rome.” When he asked the people living among the monuments who had built them, they answered: “It is the work of the King of the Angels”; “It is the work of giants”; even, “They built themselves.”

I knew the layout of Angkor Thom by heart from a guidebook by the archaeologist Henri Marchal, published in 1928. The city is walled and moated, accessible by five monumental stone gateways surmounted by towers with four identical faces at the cardinal directions, smiling serenely into the jungle. The identity of the Angkor face, which is found everywhere in the ruins, remains a mystery. It has been variously identified with the Hindu god Brahma, the popular bodhisattva Lokesvara, and Jayavarman VII, the twelfth-century king who built many of the principal temples. The image could have served all three cults at once.

At the center of Angkor Thom rises the Bayon, an eccentric labyrinth of corridors and courtyards described by Loti as “this basilisk phantom, a bridge to ancient times, constructed with cyclopean blocks.” Literally a labyrinth: wandering around the Bayon, one easily gets lost or comes to a dead end. The walls are covered with fine bas-reliefs depicting scenes of war and domestic life, interspersed with hundreds of images of elegant apsara, usually translated as “celestial nymphs.” The upper level is crowded with four-faced towers like those on the city gates. Even authoritative sources disagree as to how many towers there are: most say fifty-four, while one scholar goes as low as thirty-seven surviving of the original forty-nine. I tried to count them, but no matter how methodically I went about it, I kept losing track, just as the driver had warned me I would. I returned to the hotel for lunch, where I was attended by a dozen adolescent boys wearing dirty white shirts missing buttons and skinny black ties.

As the afternoon sun declined, Ciochon had recovered sufficiently to accompany me to Angkor Wat. Called the largest stone monument and the largest religious building in the world, it occupies a square mile, constructed from pale gray fine-grained sandstone carved with a delicacy that exceeds the other ruins of Angkor. The central tower takes the shape of a colossal lotus bud, rising to a height of two hundred feet, lording over the forest for miles around. We roamed the grounds of the temple guided by a demented old man with a stiff brush of white hair named My Huy, who said he had been trained by French archaeologists. He told me that he had survived the Khmer Rouge era by lying awake in bed for hours every night, continually gripping and turning a rough stick in his hands, which raised calluses that enabled him to pass for a peasant and avoid summary execution as an “intellectual.” A pair of cowherds, boys no older than ten, drove their charges at a discreet distance behind us, the thok-thok of wooden cowbells setting a gentle, strolling pace.