PUEBLA, MEXICO.- Archaeologists working at Teteles de Ávila Castillo in the Sierra Norte of Puebla have confirmed that a monumental architectural complex at the site functioned as a solar observatory more than 2,500 years ago, a discovery that could reshape understanding of astronomical knowledge and cultural connections in ancient Mesoamerica.

Research conducted by Mexico's National Institute of Anthropology and History (INAH) indicates that the complex, known as Group E or Tetelihtic, was deliberately laid out according to observations of the sun, surrounding mountains and broader astronomical horizon.

According to the archaeological team, the site may represent the oldest known complex of its kind in Mexico and the first documented outside the Maya region. Its design has been compared with the celebrated Group E complex at Uaxactún in Guatemala's Petén region, one of the best-known examples of early Mesoamerican architecture associated with astronomical observation.

"The architecture of Teteles de Ávila Castillo speaks to us of societies that developed astronomical knowledge and incorporated it into the organization of their ceremonial spaces," Mexico's Secretary of Culture, Claudia Curiel de Icaza, said. She added that the research helps reveal the depth of scientific knowledge developed in different parts of Mesoamerica.

The complex stands east of the site's Great Plaza and consists of a quadrangular courtyard framed by two platforms. The eastern structure extends approximately 90 meters from north to south and 40 meters from east to west. A smaller western structure, measuring about 46 by 27 meters, appears to have served as the principal observation point.

Alberto Diez Barroso Repizo, director of the Teteles de Ávila Castillo Archaeological Project, said the settlement is an exceptional example of pre-Hispanic urban planning shaped through close observation of both the landscape and the sky.

The complex dates to the Middle Preclassic period, approximately 1000-600 BC. Its general plan closely resembles Group E complexes known from the Maya world, although the Teteles example is considerably larger than Uaxactún's.

What makes the Puebla site especially unusual, however, is the way it appears to have been used. Rather than placing the equinoxes at the center of the elongated eastern platform, observations suggest that the complex helped mark the beginning of the Mesoamerican calendar in February and the harvest season in October.

Researchers have also confirmed that the eastern platform functioned as a type of solar calendar. From the observation area, the movement of the rising sun could be followed as it shifted across the horizon through the equinoxes and solstices.

The findings may also have broader implications for the study of cultural relationships between Maya and Huastec peoples. Archaeologists believe that a Maya presence at Teteles could reach back to the first millennium BC, potentially providing evidence relevant to the debated ethnolinguistic connections between the two groups.

The research team is also examining possible astronomical and religious associations within the site. One hypothesis links the orientation of its largest structure with Canopus, the second-brightest star in the night sky, and with the Nahua goddess Nantehuitz, whose name has been translated as "our mother of the south."

Another major line of inquiry concerns the possible origins of Totonac culture. Archaeologists believe Tetelihtic may preserve evidence of populations ancestral to the Totonac communities that would later flourish at sites including Yohualichan in Puebla and El Tajín in Veracruz.

Tetelihtic appears to have been occupied from around 900 BC until approximately AD 100. As major centers such as Cantona, Cholula and Teotihuacan began to emerge, the settlement was partially abandoned, although offerings dating from AD 100 to 600 suggest that the ceremonial precinct continued to retain religious importance.

A later Totonac offering dating to approximately AD 600-900 was found in one of the site's platforms, indicating that the place remained significant even after its original settlement had been abandoned.

The discovery adds Teteles de Ávila Castillo to a growing body of evidence showing that sophisticated astronomical observation was deeply integrated into the architecture, ritual life and urban planning of ancient Mesoamerican societies.