A palace at the top of the world

In the mountains of Peru, entire cities have been lost since they were abandoned by the last Incas five centuries ago. Hugh Thomson - young, British, and with no idea what he wanted to do with his life - found the idea of discovering one irresistible.

Thomson takes us with him on his "Exploration of the Inca Heartland," where he succeeds in putting several lost sites in their rightful places on the map. But the quest soon becomes far more ambitious than an effort to locate ruined cities by traversing roadless mountains in landslide country, or pushing through tropical forests so lush that a hiker can pass within a few feet of a large stone building without seeing it.

Thomson casts his book as a travel memoir, and it would make an interesting read if it were no more than that, but it is much, much more. Belying his casual, kid-with-a-backpack approach, Thomson reveals a sophisticated grasp of Andean history, a canny understanding of the complex encounter between Indian and Spaniard, and a firm grasp of the interaction between human society and the Peruvian mountains.

The Cobos family, two generations of whose members guide Thomson's explorations, follow the ancient Andean practice of having a farm at 10,000 feet, and another in the tropical forest. They move regularly between the two, bringing mountain-grown grain and potatoes to their lowland farmhouses, and carrying fruit upslope.

The Incas were ruthless conquerors. But Thomson argues that despite their undoubted prowess at arms, the imperial success of the Incas was the result, less of might than of the fact, that within their vast empire the rule of law and an excellent road system allowed the peoples they subjugated to exchange the produce of the high mountains for the fruits of the humid lowlands. Is it better to be independent, or to be well-housed, well-clothed, and well-fed? he asks.

Well-built in stone, Inca roads still traverse the Andes. Unlike European roads that zigzag up mountains to enable horses to walk up a gradual incline, these Inca roads are dizzying ascents of hundreds of stone steps leading straight to the top. Llamas can climb stairs.

Pack animals, meat supply, and providers of fine wool, llamas fed the Incas, clothed them, and provided the transport that made empire possible. Llamas were the muscle and fiber of the empire, and they flourish on the grasses of high Andean pastures. This explains why it was practical for the Incas to have their capital at Cuzco, even though at 11,207 feet above sea level many visitors suffer altitude sickness.

An emperor can put his summer palace anywhere he likes, so why did the Incas build Machu Picchu on a remote mountain top? Visitors reach the 13,000-foot-high site after a long climb up a breathtaking flight of stairs. The Inca Emperor, of course, was carried up in his elegant litter.

Thomson thinks that the Incas chose this spot for the same reason that tourists take the long flight to Calgary to stay at the Banff Springs Hotel: love of the mountains and of mountain views. The resort towns of the Inca elite were placed on those mountain ridges that offer the most magnificent views, and Inca Wasi is the most spectacular of them all.

One of the things that makes Inca resort cities so visually compelling is that they contain no working-class housing. Servants lived in modest villages located downslope.

Mountain resorts like Machu Picchu and Inca Wasi are comprised entirely of the palaces of the rich, expertly dressed stone buildings set amid stone terraces and plazas.

Below Inca Wasi, the Incas built a dam to create a mountain lake. At Inca Wasi there is "a terrace with nine trapezoidal niches rising up to a two-stories building, steeply gabled, positioned on a knife-edged ridge," Thomson writes. "On the other face of the valley was a monumental rock, which had a striking white spot on its summit. From Inca Wasi, this spot was perfectly reflected in the lake directly below, with an odd ghostly effect of white on water. The building was placed to be precisely on the sight-line of this reflection. If you moved just a few feet away from the centre of the terrace the reflection was lost."

Thomson's argument about the Incas' motives is made more compelling by the fact that we are unaccustomed to thinking of pre-Columbian civilizations as peers.

The Incas, after all, dressed the mummified remains of their dead emperors in elegant robes, retinues of servants attended their needs, and they were carried to the central plaza to witness state celebrations. Yet these people who lacked a written language, and had no knowledge of the wheel and no iron, built mountain palaces sited with an aesthetic sensibility that meshes precisely with our modern notions of the sublime.

Beyond the thrill of an adventure story well told, the insightful glimpses into ways of organizing a great empire utterly unfamiliar to Western thought, and the pleasures of Thomson's wryly self-deprecating humor, the delight of the "White Rock" lies in the realization that a people as ancient and primitive as the Incas could so exactly share our sense of the beautiful.

• Diana Muir lives in Newton, Mass., and is the author of 'Reflections in Bullough's Pond: Economy and Ecosystem in New England' (University Press of New England).