Huayna Picchu is about 2720 meters above sea level which makes it around 360 meters higher than Machu Picchu. After signing in into a guest book, it is a steep climb up, and the relatively thin air wears one off quickly.
The Inca build temples and terraces on its top which they connected with trails to Machu Picchu. They run up along the side of Huayna Picchu. Legend has it that the buildings on the top were inhabited by a high priest, and local virgins.
The Temple of the moon is located on one side of the mountain at an elevation below that of Machu Picchu. It is believed that it once housed mummies. My schedule however did not allow to visit it.