In August, 2007, I joined two friends for an adventure in the Andes Mountains in Peru. We spent a couple of days acclimating to the 11,000 ft above sea level altitude of Cusco and then went on a 4 day hike from the town of Cachora to the Inca ruins at a place called Choquequirau which is located in the same region as Machu Picchu. It is said that the son of the Inca king who built Machu Picchu built Choquequequirau. It was a very strenuous 20 mile hike over two days ranging between 10,000 and 5,000 feet in altitude.
Here is an excerpt from InkaNatura Travel:
Choquequirau
The Cradle of Gold.
"Choquequirao sits in the saddle of a high Andean ridge, 3000m./10,000 ft. above sea level and 1,500m./5,000 ft. above the roaring waters of the Apurimac River. Ringed by spectacular snow-capped peaks and flanked by plunging, thickly forested slopes, the city is an inspiring example of an elite Inca ceremonial center, dedicated to the worship of the mountain gods, the river and the elements of nature.

Choquequirao has been called “Machu Picchu’s sacred sister”, because of the striking similarities of design and ceremonial architecture to its famous counterpart above the Urubamba Gorge. Yet it remains an enigmatic place whose history is a matter of speculation. One theory of its origins holds that it was a royal estate built for the emperor Topa Inca, perhaps in an attempt to rival his father Pachacuti’s spectacular domain at Machu Picchu.
For centuries Choquequirao lay shrouded in obscurity, protected by its remoteness. Unlike Machu Picchu, people knew it was there – it was first mentioned in a Spanish document of 1710, later visited by various explorers and treasure hunters, and roughly surveyed in the 19th century by the French consul in Lima, Leonce Angrand. Finally, in 1909, the indefatigable U.S. explorer Hiram Bingham –the future scientific discoverer of Machu Picchu -- explored and mapped the site.

Today we can trek to Choquequirao via a modern footbridge across the Apurimac River. The journey is as awe-inspiring as ever, taking us through an astounding range of ecological zones, from Andean farming valleys, descending through a hot and arid canyon environment featuring kapok trees, cactus and agaves, and climbing again to a region of lush cloud forest, beneath the dizzying snowcaps of the Cordillera Vilcabamba."