Each "taula" - named after the Catalan word for table - is formed by two massive stone blocks arranged in the shape of an upright "T". The taulas face an opening in a surrounding ring of stones, and all but one of the 30 structures on Menorca face roughly south.
"It has long been known that these taulas were sanctuaries," says University of Cambridge archaeoastronomer Michael Hoskin, citing the large number of bones from sacrificial animals that litter the sites.
But the sites were also home to a few intriguing bronze statues, including a bull, an Egyptian figurine with an inscription in hieroglyphics reading, "I am Imhotep the god of medicine" and horse hooves. The latter is particularly curious as there is no known horse god in ancient Mediterranean cultures.
Hoskin was invited to study the sites' orientation to understand the significance of both the bronze statues and why no taulas are found on the nearby island of Mallorca. The taulas' southern orientation - facing the sea or looking down from a hillside - gave him an important clue.
"What was near the southern horizon that was of interest?" Hoskin wondered. Today the answer is not much. But over time, gravitational tugs from the Sun, Moon, and planets make the Earth wobble on its axis like a spinning top.
For this reason, the night sky would have looked slightly different in 1000 BC, when the taulas were constructed. At that time, the entrance to the taulas framed the seasonal rise of a constellation known as Centaurus by the ancient Greeks. Today, it is split into the constellation of the Southern Cross, followed by the bright stars Beta and Alpha Centauri.
In Greek mythology, the Centaur - who had a man's head and a horse's body - taught medicine to Asclepius, the god of medicine.
Myths circulated around the Mediterranean and Near East even before
the taulas were made and the different cultures engaged in a lot
of trade, "so it is entirely possible - but not proven, of
course - that the Menorcans had a similar view of Centaurus [as
the ancient Greeks]," Hoskin told New Scientist.
The association with healing could explain the bronze hooves - which could be the remains of a statue of the Centaur, the Egyptian medicine god figurine - possibly left by an Egyptian sailor - and even the absence of taulas on neighboring Mallorca.
"Menorca is flat and you can see the Southern Cross, etc., from almost any location," Hoskin explains. Settlements on mountainous Mallorca, on the other hand, were located in valleys "from which the Cross was invisible because it was screened by the surrounding hills".
Steve McCluskey, a historian of astronomy at West Virginia University in Morgantown, West Virginia, US, says Hoskin's astronomical and archaeological evidence "combine to provide strong indications of a healing cult at this site".
McCluskey also said Hoskin has "fundamentally transformed" archaeoastronomy
by showing that the builders of these monuments were little concerned
with the "highly precise orientations that had formerly been
the touchstone of archaeoastronomical investigations". Pointing
their constructions in roughly the right direction appears to have