Staff members of Mexico's Anthropology and History National Institute (INAH, by its acronym in spanish) carry a sacrificial stone found in the Sacred Spot of Tenochtitlan, in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. Some 45 human skulls and 250 human jaws were discovered by INAH in the ceremonial temple of Tenochtitlan's Sacred Spot. Buried under this group of human skulls and jaws were a sacrificial stone and another five fractured skulls. Archaeologists assume that, the sacrificial stone and the human remains were part of a "tzompantli", an Aztec monument to expose the skulls of the slaugtered. (Xinhua/Rodrigo Oropeza)

A human skull found in the Sacred Spot of Tenochtitlan is presented by staff members of the Mexico's Anthropology and History National Institute (INAH, by its acronym in spanish), in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. Some 45 human skulls and 250 human jaws were discovered by INAH in the ceremonial temple of Tenochtitlan's Sacred Spot. Buried under this group of human skulls and jaws were a sacrificial stone and another five fractured skulls. Archaeologists assume that, the sacrificial stone and the human remains were part of a "tzompantli", an Aztec monument to expose the skulls of the slaugtered. (Xinhua/Rodrigo Oropeza)

A sacred tree found in the Sacred Spot of Tenochtitlan is introduced by Anthropology and History National Institute (INAH, by its acronym in spanish), in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. The new discovery which contains an oak trunk was made in May 2012. (Xinhua/Rodrigo Oropeza)

Staff members of the Anthropology and History National Institute (INAH, by its acronym in spanish) talk with each other near a sacred tree in the Sacred Spot of Tenochtitlan, in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. The new discovery which contains an oak trunk was made in May 2012. (Xinhua/Rodrigo Oropeza)

A human skull found in the Sacred Spot of Tecnochtitlan, is introduced by Mexico's Anthropology and History National Institute (INAH, by its acronym in spanish) in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. Some 45 human skulls and 250 human jaws were discovered by INAH in the ceremonial temple of Tenochtitlan's Sacred Spot. Buried under this group of human skulls and jaws were a sacrificial stone and another five fractured skulls. Archaeologists assume that, the sacrificial stone and the human remains were part of a "tzompantli", an Aztec monument to expose the skulls of the slaugtered. (Xinhua/Rodrigo Oropeza)

A staff of Mexico's Anthropology and History National Institute (INAH, by its acronym in spanish) works on a human skull found in the Sacred Spot of Tenochtitlan, in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. Some 45 human skulls and 250 human jaws were discovered by INAH in the ceremonial temple of Tenochtitlan's Sacred Spot. Buried under this group of human skulls and jaws were a sacrificial stone and another five fractured skulls. Archaeologists assume that, the sacrificial stone and the human remains were part of a "tzompantli", an Aztec monument to expose the skulls of the slaugtered. (Xinhua/Rodrigo Oropeza)

A staff of Mexico's Anthropology and History National Institute (INAH, by its acronym in spanish) introduces human skulls found in the Sacred Spot of Tecnochtitlan, in Mexico City, capital of Mexico, on Oct. 5, 2012. Tenochtitlan was the capital of the Aztec Empire, before the spanish conquest 500 years ago. Some 45 human skulls and 250 human jaws were discovered by INAH in the ceremonial temple of Tenochtitlan's Sacred Spot. Buried under this group of human skulls and jaws were a sacrificial stone and another five fractured skulls. Archaeologists assume that, the sacrificial stone and the human remains were part of a "tzompantli", an Aztec monument to expose the skulls of the slaugtered. (Xinhua/Rodrigo Oropeza)