Choquequirao is often referred to as a "sister city" to Machu Picchu. The hike to Choquequirao is quite difficult and far fewer people go there than the more popular Machu Picchu. Machu Picchu was amazing, but the feeling of isolation and lack of tourists made Choquequirao a more impressive site to me. A recent write-up on Choquequirao in The New York Times is included in the link below.
