Alentejo Megaliths

9 08 2011
Évora Almendres Cromlech

Évora Almendres Stone Circle. Photo credit: Mick L

I’m moving offices, so I’ve been sorting through the stacks of paper that have failed to find a home in a file folder over the past two years. On top of my stack of archaeoastronomy articles was an analysis of the megalithic enclosures in the historical province of Alentejo in south-central Portugal.* I saved it because I thought it might be relevant to my dissertation (it wasn’t); I re-read it because I had been thinking about the distribution of megaliths across northern Europe while writing about Stonehenge knock-offs yesterday.

The Alentejo stretches south from the Tejo River to north of the Algarve (Faro District). The Évora district occupies the middle section of the Alentejo. Within the Évora district are twelve known stone enclosures built during the Middle Neolithic period (sixth to fifth millennia B.C.).  Most of the enclosures were built in a horseshoe shape, with openings oriented to the east. The smallest complex, Vale d’el Rei, has twelve menhirs in a simple horseshoe shape; the largest, Almendres, has 94, with a more complicated configuration.

Site Plan, Almendres. Image credit: Pedro Alvin

Site Plan, Almendres. Image credit: Pedro Alvin

A new archaeological survey was conducted of the twelve known sites, including both the location of the extant menhirs and their relationship to the larger landscape (distance to horizon profile, horizon marks, maximum slope, axis of symmetry).** The survey demonstrated that eight of the twelve sites had axes with orientations within a range of 35.4° of azimuth, in approximately the eastern direction. The research team concluded that the probability of this common orientation occurring by chance was very low (~7 x 10^-7), and there could only be two explanations for it:

“either an astronomical target (Sun, Moon, or planets, based on the possible declinations for 6000-5000 B .C.) or a construction following the slope, turned to the direction of the far horizon, since we verified a Pearson product-moment correlation coefficient of .7 between the azimuth of the symmetry axis and the azimuth of the steepest slope.” (p.7)

I’m not sure of what I think of this first conclusion. What about the 1/3 of the sites that didn’t exhibit this commonality? And what about Xarez, which was excluded from the study because of controversial excavations (see **, below), but may have had a different configuration that then twelve sites included the study? At any rate, this initial conclusion motivated the research team to further analyze their data to determine which of the two options was most probable.

Évora Almendres Cromlech.

Évora Almendres Stone Circle. Photo credit: Phillip Capper

The data crunching is impressive and I direct you to the published article to read the description of their probability models (I am not qualified to comment on the validity of Bayesian analysis in this case). Ultimately, the team discarded the possibility that the structures had been positioned in regard to slope. That left them with option two—the stones were arranged in response to an astronomical target. But which target?

It’s possible that the stones had a lunar association—the crescent symbol is engraved on several menhirs in Almendres, Pórtela de Mogos, and Vale Maria do Meio. Most of the engraved surfaces face the east, which could indicate a lunar orientation. On the other hand, it could also indicate a solar orientation, much like that exhibited by the dolmens (stone tombs) in the same region. The builders of the monuments were likely hunters-gatherers-farmers and may have needed the stones as a tool for telling time or marking the seasons. Or maybe not. The authors seemed to hedge their bets, which is common when writing about ancient architectures, but didn’t leave me feeling convinced of their conclusions.

That being said, the tables that accompanied the article are quite valuable. They include menhir statistics (size, location, position, decorations), enclosure statistics (latitude, azimuth of steepest slope, slope, symmetry axis aximuth, declination, horizon altitude), elevation profiles and horizon features of the sites in the study, and site plans for the Almendres, Vale Maria do Meio, Portela de Mogos, Tojal, Cuncos, Sideral, Fontainhas, and Val d’el Rei enclosures. You can also see site plans for many of the enclosures, drawn by Pedro Alvin, at (scroll to the bottom of the page).


*Fernando Pimenta, Luís Tirapicos, and Andrew Smith. “A Bayesian Approach to the Orientations of Central Alentejo Megalithic Enclosures.” Archaeoastronomy 22 (2009): 1-20.

**The archaeological survey did not include the stone circle of Xarez, citing controversial excavation and reconstruction techniques as described in: Manuel Calado, Menires do Alentejo central. Genese e evoluçâo da paisagem Megalitica regional, Lisboa. 2004. Unpublished Ph.D. dissertation. University of Lisbon.

Stonehenge Revisited

8 08 2011
Stonehenge Aotearoa Stormy Sky

Stonehenge Aotearoa Stormy Sky. Photo credit: Chris Picking

True story: when I first visited the Stonehenge Memorial at the Maryhill Museum of Art in Washington State, I didn’t know it was an imitation. I usually attribute my ignorance to my age at the time and my upbringing in a rural area in the dark ages before the Internet, but even with those allowances, you’d think I would’ve learned at some point in grade school that Stonehenge was at Avebury on Salisbury Plain.* Luckily, I was smart enough to keep my mouth shut on the way to Maryhill, where the signage explained that the monument was a replica.

There are so many Stonehenge replicas in the world, some more accurate than other. Of the less accurate but more entertaining variety, Carhenge is probably the most famous. I’ve managed to drive through the State (uh, Official Commonwealth) of Virginia several times without ever stopping at Foamhenge. And, no, I wasn’t at Glastonbury in 2007 to see the construction of Banksy’s Loohenge.

More interesting to me are the models that attempt to establish some relationship between the architecture and astronomy. Although the sentiment behind the Maryhill Stonehenge was misplaced, as a structure, it is carefully designed and well-built, with the altar stone aligned with the sunrise at the summer solstice. Similarly, although Stonehenge Aotearoa was built at a similar scale to the structure at Salisbury, it was aligned for the southern skies. For example, the heel stones of the henge mark the rise and set points of the sun at the midsummer and midwinter solstices, and the autumn and spring equinoxes. In addition, a well-placed obelisk points to the celestial south pole, acting as an axis mundi for the night-time visitor. Specific to the Aotearoa site are stone representing the Pleiades, or the “Seven Sisters”. Maori refer to this group of stars as “Matariki” and use its position mark the beginning of a new year in late May/early June.  To the south-west of this group of stones stands a single marker stone indicating the location of Matariki’s rise.

So, I find the models that attempt to investigate/explain the links between astronomy and architecture more interesting than things like “Butterhenge” or “Peepshenge”. Most interesting of all, however, are the many “real” henges that I only learned about in heritage management courses in graduate school:  Woodhenge, Seahenge, the Ring o’ Brodgar, Stenness (Orkney); the Thornborough Henges, Yorkshire; the Mayburgh Henge, Cumbria; and many others. They intrigue me for the obvious reasons—what do they mean, who built them, how were they built—but as a historian with a research interest in cultural heritage studies, I also find them interesting test cases for public and state preservation policy. How do you approach the management of a wood henge that has been almost completely eroded by the sea? Who has the right to access the inner circle of Stonehenge? Can you copyright a neolithic stone structure?

*By the way, don’t listen to all those people who complain about Stonehenge being a tourist trap and a disappointment just because you can’t touch the stones or buy a decent cup of coffee at the site. Stonehenge is awesome, case closed.