The Celestial Carcassonne
Peyrepertuse sits on a limestone ridge 800 meters high in the French Pyrenees. Its name comes from the Occitan "Pèirapertusés," meaning "pierced rock." The fortress is so vast, stretching over 300 meters along the crest, that it is often called the "Celestial Carcassonne." Archaeological evidence shows Roman occupation at the site from the 1st century B.C., though the first historical records of the castle date to 806.
During the Albigensian Crusade in the 13th century, a campaign against the Cathar heresy, the fortress was an important strategic point. Its owner, Guillaume de Peyrepertuse, was excommunicated in 1224 for refusing to submit to the crusading forces. He eventually surrendered the castle to the French crown in 1240 without a fight. Following this, King Louis IX of France invested heavily in the structure. In 1242, he ordered the fortification of the lower castle and the construction of a second, higher castle—the Sant Jordi (Saint George) keep—which was completed around 1251. This turned Peyrepertuse into a formidable royal fortress on the border with the Crown of Aragon, a role it maintained until the Treaty of the Pyrenees in 1659 shifted the border south.
Bioarchaeology of a Siege
The stones of Peyrepertuse record military history, but the soil within its walls contains human stories revealed by chemical analysis. Bioarchaeological studies on skeletons found within the castle show evidence of the inhabitants' diet. The method used is stable isotope analysis of bone collagen, the main protein in bone. This technique relies on the principle "you are what you eat," where the chemical signatures of consumed foods become recorded in skeletal tissues.
Scientists measure the ratios of stable isotopes of carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N). These ratios differ based on the types of plants and proteins consumed. Most plants, including wheat, barley, fruits, and vegetables common in the Mediterranean, are C3 plants and have a distinct carbon isotope signature. C4 plants, like millet, are adapted to warmer, drier climates and have a different signature. Nitrogen isotopes, meanwhile, indicate an organism's position in the food chain, or trophic level; values increase from herbivores to carnivores.
Analysis of the Peyrepertuse skeletons indicates a diet based predominantly on terrestrial C3 plants. This suggests the garrison and inhabitants consumed wheat, barley, and other local Mediterranean agricultural products. The nitrogen isotope values show a significant intake of animal protein. Even during periods of military conflict and potential siege, the data shows no evidence of a shift to C4 plants like millet, which were often consumed during times of famine in other parts of medieval Europe. The findings suggest that the fortress's supply lines, even under pressure, allowed continued access to a standard Mediterranean diet rather than forcing a reliance on starvation foods.