This site features a two-story kallanka, or Inca hall, that is nearly 40 meters long and topped off by a well-preserved third story of adobe—it is easy to imagine this adobe painted, as were the buildings in Cusco, and topped off with a pyramid of thick thatch.
There are also terraces, a square, an Inca gate, and many other rougher buildings within a few hundred meters of the hall. The whole site commands a small plateau, 800 meters above the Sacred Valley, with spectacular views.
This was probably the royal estate once known as Caquia Jaquijahuana, where, according to myth, Inca Viracocha hid when the Chancas threatened to invade Cusco  in 1438. One of his sons, who later renamed himself Pachacútec, rose up and defeated the Chancas, thus beginning the meteoric rise of the Inca. After the conquest, the Spaniards found a mummy at this site—said to be that of Viracocha.
Reaching Huchuy Cusco is not easy, but it’s worth the effort. The shortest way to get there is a three-hour, uphill hike from Lamay, a village between Pisac  and Urubamba . The entrance to the footbridge that crosses the Río Urubamba is marked with a large blue sign from the National Institute of Culture.
Another highly recommended option is to approach Huchuy Cusco from the opposite direction in a two-day hike across the high plains from Cusco. The trip starts at Sacsayhuamán in Cusco  and follows the original Inca Trail  to Calca, heading past finely wrought canals, villages, and several 4,000-meter passes.
The total trip is 17 miles, including the final descent to Lamay, where you can catch a bus back to Cusco  via Pisac . Both trips are described in detail in Peter Frost’s Exploring Cusco. For either route, bring plenty of water and food as there is little along the way.