The canyon seems bottomless. From the lookout where the trail begins, the Apurimac River is a greenish-white ribbon speckled with tiny black dots, which you know are house-size boulders. Beyond the canyon, the massive snow peaks of the Cordillera Vilcabamba seem to fill the sky.

The Inca terraces at Choquequirao are dimly visible on a ridge to the north-east, green and hazy in the distance. To reach them it will take two days of hard walk.

Choquequirao is one of those places we have always known about, yet never rally known. Unlike Machu Picchu , its name has been mentioned since colonial times. Treasure hunters went there occasionally from the early 18th century onwards, lured by its tantalizing name - "Cradle of Gold". The French scholar Leonce Angrand drew the first maps in 1847. Hiram Bingham went there in 1909, two years before he reached Machu Picchu .

Yet Choquequirao was extremely difficult to reach, its access barred by the roaring waters of the Apurimac, which could only be crossed by means of an oroya - a death-defying cable and basket. All that changed when the Peruvian government built a sturdy footbridge near Cachora in 1994.

Even today the journey is long, but for the growing army of those who love the challenge of the Andes it is everything one could hope for. It starts in Cusco, with a scenic 4 or 5 hours drive along the highway towards Abancay, first crossing the rolling Pampa de Anta with vistas of the Urubamba range, the Salcantay Mountain, and then a stupendous series of hairpins in the descent to Limatambo and the Apurimac. A steep ascent from the river leads past fields of white anise flowers in the balmy climate of Carahuasi, while along the way you can visit the elegant Inca stonemasonry at Tarawasi and the unique Inca sculptures of Sayhuite. The road is paved until the turn-off to Cachora, where a series of hairpins descends into a high Andean valley sloping once again towards the mighty Apuimac canyon.

Cachora is the place to rent mules, guides and saddle horses. The trail is good, but the journey calls for a 4,300 ft. descent in altitude to the Apurimac River, followed by a climb of 4,920 ft. to the Inca ruins. The views are spectacular, and the ecology passes through those radical Andean changes, reaching a hot and arid canyon-floor ecology of tall cactus and thorn bushes at the river.

Most hikers camp the first night at the small, wooded site of Chiquisca, about 1,300 ft. above the river. Next day you descend more steep zigzags to the river, and cross the footbridge. It is vital to leave early, since the canyon becomes extremely hot as the day wears on, and the only way to avoid this is to gain some altitude before mid-day. As you climb the north bank of the Apurimac you reach a world of green slopes and remnant patches of cloud forest which grow denser and less disturbed by humans as you reach Choquequirao. Scattered farmers occupy the few areas of semi-level terrain along the way, including one who grows sugar cane and distils his own liquor - available for sale!

You see the Inca ruins across a deep ravine long before you reach them, sitting on a ridge, below the forest-covered mountain, gazing down into the immensity of the canyon - a setting more than equal to the splendor of Machu Picchu .

Comparisons with the latter seem inevitable. The place would almost seem to have been constructed to rival that exotically located settlement. Like Machu Picchu , it bears the characteristics of an elite ceremonial center, and certain architectural details suggest that, in fact, the settlement may have been constructed for the emperor Topa Inca.

The present campsite is a sloping area some 20 minutes below the ruins.

Choquequirao is larger than anyone realized until recently, since forest still conceals so much of its ruins. But the arriving visitor reaches the heart of the site via its most prominent feature, a series of enormous, beautifully-constructed terraces. The central plazas display the typically careful Inca planning, with tall, two-story residential buildings, assembly halls, and complexes of ceremonial baths and temples.

The broad ceremonial platform overlooking the site gives superb views of the surrounding snow peaks and a sweeping panorama of the Apurimac canyon. condors soar low across the ruins each afternoon, and bears are sometimes seen on the pathways near the site. The unforgettable beauty and fascination of the Andes is as powerful here as in few places in Peru.

You must simply retrace your steps to take the standard return journey to Cusco - but do not miss a delicious swim in the Apurimac, which you will inevitable cross in the heat of the afternoon.