A trophy rack of sacrificed human skulls was found on Thursday at Mexico City's Templo Mayor Aztec ruin site, according to The New York Times.

The trophy rack is known as a "tzompantli" in the Aztec language of Nahuatl, Reuters reported.

The "tzompantli" is where ancient Aztecs would display severed heads. The heads would be suspended on vertical posts by poles pushed through the sides of the head.

The skulls were those of sacrificed warriors from rival kingdoms, killed at the tops of religious temples located close to the display site. The skulls themselves were bleached white before being displayed, according to Reuters.

So far, 35 skulls have been found on the 112-foot-long, 40-foot-wide rack. However, it's believed that more will be found in underlying levels, according to Discovery News.

Archaeologists believe that the skulls belonged to Huey Tzompantli, the Great Tzompantli of Tenochtitlan. The area where these skulls were found, Mexico City, is estimated to contain 60,000 sacrificed skulls.

The Aztec empire ruled over a large expanse of land, from the Gulf of Mexico to the Pacific Ocean, for almost 100 years. Their reign ended between 1519 and 1521 upon arrival of the Spanish.