About 23 tombstones dating back to 15th century have been excavated at the ancient site of Tenochtitlan in the central part of Mexico City, the UNESCO's World Heritage Centre said in a statement Friday.

Founded in 1325 in the Valley of Mexico, Tenochtitlan, the modern day Mexico City, served as the capital city of Aztec Empire that ruled the region from 1428 until they were defeated by Spain in 1521.

The new finds highlight, without a doubt, two histories of two different cultures in Tenochtitlan, the World Heritage Centre added, pointing towards the effects of Aztec and Spanish cultures on Tenochtitlan.

The tombstones have carvings of snakes, prisoners, ornaments and warriors, which seem to depict the birth of Huitzilopochtli, the god of war and patron of the Aztecs, according to archaeologists from INAH-Conaculta (The Mexican National Institute of Anthropology and History and the Mexican National Council for Culture and the Arts), who found the tombstones.

The tombstones, over 550 years old, are located in front of the ruins of the Templo Mayor, the ancient temple of the Aztecs excavated in 1978. Starting in 1325, the temple had been built six times until it was destroyed by the Spanish invaders in the early years of the 15th century.

The tombstones appear to have been laid out purposefully along a path consisting of 16.7 meters long and 3.3 meters wide slabs, corresponding to one of the stages of the construction (between 1440 and 1469) of the Templo Mayor.

In September 2011, a circular platform, over 500 years old, with stone carvings of 19 snakes' heads, was discovered just near the site of tombstones. The archaeologists say the circular structure corresponds to another construction stage (1469-1481) of the sacred site.

While the archaeologists are doing further research to establish a historic connection between the new finds and the circular structure, they are hopeful of exploring the architecture of Tenochtitlan further.

Gradually we are completing the architectural topography of ancient Tenochtitlan, which according to the chronicles, comprised of 78 Prehispanic buildings in the holy place.