Písac is a Peruvian village in the Sacred Valley on the Urubamba River.
The area is perhaps best known for its Incan ruins, known as Inca Písac, which lie atop a hill at the entrance to the valley. The ruins are separated along the ridge into four groups: Pisaqa, Intihuatana, Q'allaqasa, and Kinchiracay. Intihuatana includes a number of bathes and temples. The Temple of the Sun, a volcanic outcrop carved into a "hitching post" for the Sun (or Inti), is the focus, and the angles of its base suggest that it served some astronomical function. Q'allaqasa, which is built onto a natural spur and overlooks the valley, is known as the citadel.
The hillside is lined with agricultural terraces constructed by the Inca and still in use today. These terraces were created by hauling richer topsoil from the lower lands by hand. They enabled them to produce surplus food more than would normally be possible at altitudes as high as 11,000 feet.  With military, religious, and agricultural structures, the site served at least a triple purpose. Besides a country estate, it is thought that Písac defended the southern entrance to the Sacred Valley, while Choquequirao defended the western entrance and the fortress at Ollantaytambo the northern. Inca Pisac controlled a route which connected the Inca Empire with the border of the rain forest. According to Kim MacQuarrie, Pachacuti erected a number of royal estates after he conquered other ethnic groups to remember the victories. Among these royal estates are Pisac (victory over the Cuyos), Ollantaytambo (victory over the Tambos) and Machu Picchu (conquest of the Vilcabamba Valley) . Other historians suggest that Pisac was established in order to protect Cusco from possible attacks of the Antis nations. It is unknown when Inca Pisac was built. Since it does not appear to have been inhabited by any pre-Inca civilization,