A new survey of the Valley of the Temples just outside Agrigento, Italy, reveals the 2,500-year-old temples were not deliberately aligned to the rising sun, as generally believed. A variety of factors, not all of them being astronomical, inspired the ancient architects. It seems an ancient Greek temple was built to face the setting full moon near the winter solstice.

Giulio Magli, professor of archaeoastronomy at Milan’s Polytechnic University, and colleagues Robert Hannah, at the University of Waikato, New Zealand and Andrea Orlando, at the Catania Astrophysical Observatory, conducted the research with funding from the Ente Parco della Valle dei Templi.

Akragas was one of the most important Greek colonies in Sicily, and the homeland of the philosopher Empedocles (490–430 BC). Empedocles was the first to divide matter into the four elements of earth, fire, water and air. He also observed that the moon shines with light reflected from the sun. Today the Valley of the Temples consists of the remains of ten Doric temples dedicated to Hellenic Gods, Goddesses and heroes such as Herakles, Olympic Zeus, Demeter and Persephone, Hera, Hephaistos and Asklepios.

Their orientation, as well that of all Hellenic temples, has been debated for nearly two centuries. Academics wondered whether they were aligned with astronomic events like the sunrise on specific days of the year. Magli and colleagues measured the alignment of all the Hellenic temples in the valley, and showed that at least four of them are orientated in accordance with the town’s grid along the cardinal directions--irrespective of the solar date to which they would match due to the horizon.

One of the shrines, the temple of Hera, was aligned to the stars in the Delphinus constellation. On the contrary, the temple of Zeus, one of the largest temples of the Hellenic world before earthquakes and Carthaginian raids, was orientated topographically in accordance with the street grid. According to Magli:

“Incredible as it may seem, we have been unable to find this simple explanation in the literature. We know very little about the relationship between astronomy and those secret religious rites. Alignment was widely determined by urban layout and morphological aspects of the terrain as well as religious connections. For such temples, only a general rule imposing the facade towards the eastern horizon was applied. However, they were not orientated toward the rising sun on specific days of the year. A connection with the moon-orientated temple is possible and will be at the center of further research."
With the connection to the moon established and set up for further research, Magli envisioned that solstice night:

"One can only imagine the spectacle at the temple. The full moon near the winter solstice – the longest night of the year – culminates very high in the sky and remains in the sky the longest. We can imagine a nocturnal procession coming up from the fountain sanctuary and reaching the temple, in front of which, however, there is not enough space to house worshipers. They gathered in the vast esplanade on the back of the temple. From there, they would have witnessed the spectacle of the full moon high over the hill of the acropolis.”
Their findings are published on the Cornell University physics website, arXiv.org.