The Ausangate Round
Ausangate is Peru's second highest peak and the area is spectacular for its hiking through stretches of multi-coloured mineral rock. Recently lodges have been built to enable a five-day hike around the peak that culminates with the famous views. The route is all above 15,000 feet and tops 17,000 at one point, so it is a good idea to be acclimatized to high altitude. James Henderson of A Life of Adventure (who does not do well at altitude) walked the hiking route and wrote about it in the Financial Times' magazine How to Spend it. You can read his article here, Trekking in the Andes.