In the open space to the east, there is a large wayrana. Mortars that are sculpted in a circular shape with a concave base are found in the ground. While Bingham thought they were grinders, the modern-day hypothesis is that they were filled with water and used as earthquake detectors. Another speculation is that they were mirrors to view constellations.
This area is also the acllahuasi, or the “house of the chosen ones.” If you explore the area, you will see that it has a large secure doorway. Exiting the principal door, head left to the corner and go down the stairs where you will see a tomb, known as Intimachay or Cave of the Sun.
This was an important burial site in the citadel, and it contains a window that aligns perfectly with the first sunlight of the December solstice. Next to Intimachay is a large cave that contains a well-carved altar where many remains were found.
Back up the stairs and to your left is a large rock that has a slide on it. On top you will find an altar. From here, go down the stairs to the left, following the arrows to the Temple of the Condor [1].
Links:
[1] http://www.moon.com/destinations/peru/machu-picchu/ruins-tour/temple-the-condor