This is the most famous trek in Peru. On the last morning, you arrive at the Sun Gate at sunrise, just in time to watch the first rays hit Machu Picchu. I took the above photo at 6am from the Sun Gate.

This is a tough trail, partly because a lot of it is stairs built by the Inca and partly because of the altitude. On the second day you cross one pass at 4215m (13,829 ft) and another at 4000 m (13,123 ft).

Though I have done this trail twice and enjoyed it, I recommend it with hesitation. If it is important to you to hike to Machu Picchu, visit the archeological sites along the trail and see the sun rise over the ruins at the Sun Gate (Inti Punku), then you should do this trek. However, if you would be happy taking the shuttle up from Aguas Calientes in the morning to see Machu Picchu, then consider one of the other treks.