Nice workmanlike photo, but the last time I was there I seem to remember many other more dramatic points of view. Maybe shortening the photo by eliminating some of the upper sky would improve it?
The walls are great, but the vantage point of Machu Picchu being below the other mountain range hurts this one. Maybe if you were down a level where the other man-made structures are it would be improved with Machu Picchu being over everything else.
Great composition on this shot. I love how you used the walls to frame the shot. It really adds depth to it. The colors seem a bit dull to me. Possibly a boost in the saturation would help.