Heatwaves and drought in Switzerland have revealed Roman features that had remained buried beneath fields for centuries, after traces of them appeared in withered vegetation surrounding the ancient city of Aventicum in Vaud. The phenomenon enabled archaeologists to identify the remains of thermal baths, houses and road networks, along with a structure believed to have been a temple whose features were previously unknown.
Drought marks reveal buried structures
The discovery came during the hottest and driest summer in Switzerland’s history, when the effects of climate change extended beyond falling water levels. Severe heatwaves caused what are known as “drought marks” to appear in vegetation: surface indicators that reveal differences in growth above buried buildings and structures.
The phenomenon resembles what happened when European rivers receded, exposing shipwrecks dating from the Second World War. Monitoring began after a tip from a history enthusiast, prompting a group of archaeologists in Vaud to use drones to conduct daily visual surveys of the fields surrounding Aventicum.
Aventicum, capital of Roman Helvetia
The city was the capital of Roman Helvetia and was founded 2,000 years ago after Julius Caesar defeated the local tribes. Its site now lies within the small town of Avenches. Jordan Anastasov, an archaeologist in Vaud, described the results of the work by saying: “These are the richest discoveries found in the region in the past fifty years, or at least during the last two generations of archaeologists.”
Detailed aerial images showed that most of the ruins extended across land that had never previously been excavated, expanding the known archaeological areas around the city. Aventicum reached the height of its prosperity under Roman rule before gradually declining amid waves of Germanic invasions from the third century AD.
The features that emerged in the fields provide new details about the city’s urban layout, including public buildings, residences and road routes, as well as a building that researchers believe may have been used as a temple. A team of five archaeologists is overlaying the new discoveries on the established historical maps, shading the identified sites in purple.
This process enabled the team to fill geographical gaps in the city’s maps and correct mapping errors that had remained recorded in old records for decades.
Severe drought also revealed archaeological evidence at other scattered sites across Switzerland and Europe, but interpreting it is more difficult than at Aventicum. The obstacles are linked to the remoteness of some sites and the lack of specialist research teams able to interpret the visible marks and document them in the field.
