With Cusco as their capital, the Incas took just a century or so to assemble one of the largest empires in world history.
Cusco was an essential part of Incan strategy for world domination. The word 'cusco' means 'navel' in Quechua, and Cusco needed to be truly the centre of the world, not only to the Incas themselves, but to the elite of subject lands who would be 'invited' to relocate here.
Cusco had to be the most desirable place to live: impressive, comfortable, well-supplied and orderly. Cusco needed to demonstrate that the ruling Inca was the centre of power, especially religious power.
Sun worship was widespread among the many peoples of the Andes and the coast. The Incas placed their ruling Inca as the human manifestation of the Sun. Awe-inspiring temples to the sun were built around the city, glorifying the Inca as much as they hailed the sun.
The most important of these temples is Qoricancha, the 'golden courtyard'. A temple of gold-plated floors and walls stood beside a garden where golden llamas tended by golden shepherds stood beneath golden trees.
At summer solstice the Inca sat in a special niche in the temple that caught the sun's rays. From this point ley lines radiated to hundreds of sacred sites around the valley.
Every Inca married his wife here, and every Inca's mummified body was held here. The most important idols from every conquered province were brought here and held hostage.
Qoricancha had been a sun temple for the Wari culture from Lake Titicaca (see p $$): adopted by the Incas it became the most potent site in the design of their capital. The city's new layout took the outline of a jaguar: the Incan symbol of the earth. The tail lay between two rivers diverted for the purpose. At its head was the great temple of Sacsayhuamán, and at the jaguar's loins was Qoricancha itself.
Much of the gold for Atahualpa's ransom came from Qoricancha, and then the Spanish overlaid it with their unlovely Convento de Santo Domingo. But the magnificence of Qoricancha still shines out from its impressive location and from supreme examples of Incan stonework in the temple's remaining chambers and the lower walls retained by the Spanish. It is an essential for any visitor to the city.
The great sun temple of Saqsawaman, at the jaguar's head, is an absolute must too. Massive in scale, Saqsawaman was also an enormous storage depot, a ritual parade ground, a fortress if needed, and a reservoir. Most importantly, it is a formidable presence overlooking the city-a reminder of who is in charge.
Saqsawaman's key feature is a triple wall 400m long, punctuated by zigzagging angles, perhaps representing the jaguar's teeth. The lower wall is constructed in the highest quality perfectly-fitted stonework reserved for the most important Incan buildings.
Of the numerous holy sites above Cusco, one of the best is Qenko: a prime example of the 'rock cult' in the world view of the Incas and their predecessors. An amphitheatre carved into the hill looks on to a great stone, decorated with jaguar designs and carved into a temple, with divining channels where priests foretold the future from the flow of llama blood.
Life in Incan Cusco wasn't all hard work and ritual. At Tambo Machay there are impressive Incan baths, constructed in fine stonework and fed by a spring that cascades down terraces to create a cold shower just high enough for an Inca to stand under.
Today, Cusco has spread far beyond the limits of the old Incan city. There's an airport on the outskirts, busy commercial streets, housing developments and shanty areas.
Wonderfully, the old city has kept a special atmosphere. You walk down narrow alleys, beside walls of Incan stonework. You pass a church from the earliest Spanish times, or join the locals' paseo along a splendid arcade of shops from a century ago. Quechua ladies in billowing skirts chatter on street corners, traders barrow their goods over the cobbles to the colourful St Peter's Market, where eager housewives pour over mounds of Andean vegetables (including dozens of different types of potato and maize), cheery ladies proffer unrecognisable slabs of meat, and sharp-eyed witches in small booths offer unlikely remedies to their believers.
The main square, called the Plaza de Armas as always in Peru, stands on the site of the Inca's central plaza below the ruins of Saqsawaman. Here newly-weds come from around the city to stand on the steps of the Cathedral for their photographs.
Standing on the foundations of an Inca's palace, Cusco's great Cathedral is both a grand statement of the power of Spain and the church, and an assimilation of local beliefs. The massive main door, carved with a jaguar's head, opens to a vast baroque interior. A wide nave leads to an altar made with 400kg of silver. Of the many paintings only a few are European (including a Van Dyck), others are by local artists of the Cusco school, including a grand depiction of the Last Supper with apostles tucking into roast guinea pig and chicha beer.
On a busy schedule you may have only a few nights in Cusco, but if you can spare more time you really should do so.