Researchers at the astronomical observatory next door measured something curious: the entrance of the lower hill fort faces the point where the sun rises on the summer solstice. It need not be deliberate, but the site has barely been excavated and the open questions still outnumber the answers.
What to see
There are two forts, on two promontories overhanging the Saint-Barthélemy valley: in the Middle Ages the place was described as Lignyan inter duo castellaria, Lignan between the two forts. The upper one, at 1,575 metres, keeps traces of Bronze Age huts arranged in a circle around a boulder, and a short way off a rock carved with a praying figure. The lower one, at 1,546 metres, has an elliptical dry-stone wall and buildings set radially around a square structure thought to have been a place of worship or assembly.
Visiting
The path leaves from regional road 36, between the town of Nus and Lignan; there is an information panel on the lower promontory. The two settlements were identified in 1969 by Rosanna Mollo and Franco Mezzena and were inhabited between about 1200 and 900 BC, when settlements across the Alps moved from valley floors to higher, more defensible ground.
Our editors' tip
Do not expect imposing walls: these are traces, and you have to look for them. Pair the climb with the observatory at Lignan, right next door, which explains better than any panel why the sky matters so much up here.