Aventicum: Drought Reveals Hidden Roman Baths in Switzerland

Switzerland's hottest summer on record has handed archaeologists their richest discoveries at a Roman site in at least fifty years. As crops withered around the small town of Avenches, the buried outlines of Aventicum — once the capital of Roman Helvetia — rose to the surface: thermal baths, houses, roads and a possible temple, mapped from the air by a five-person team, according to Reuters.

The team, working for the canton of Vaud, was tipped off by a history enthusiast and spent the summer flying a drone over the fields, taking daily images from June through August 2026. The archaeologists then superimposed the discoveries onto their maps in purple, filling in blank spaces and correcting mistaken markings in parts of the ancient city that had not previously been mapped from the air.

Reading the fields like an X-ray

The technique behind the discovery is as old as aerial photography and as simple as dead grass. Buried stone walls drain water and hold heat differently from the soil around them, so the vegetation growing above them withers first in a drought. Those brown outlines, known as parch marks, sketch streets, buildings and baths across a green field like an architectural drawing. Aerial surveyors have used the trick since Second World War-era reconnaissance photos, but it only works when the weather cooperates — and the summer of 2026 cooperated dramatically.

Jordan Anastassov, the archaeologist for Vaud, called them the richest discoveries made at the site in the last fifty years, at least over the last two generations of archaeologists. His colleague Hugo Amoroso said the team is now asking really interesting questions it would not otherwise be asking.

The finds are fragile in a different way than buried artifacts: some of the traces captured over the summer vanished after fields were mowed and temperatures dropped, though the perimeter of a newly identified pool in the baths is still visible in a partially withered alfalfa field as unseasonably warm weather has persisted into September 2026. Pierre Blanc, the director of excavations for the site, summed up the mood by saying the team would not wish for droughts, but planned to make the most of this one and keep looking. The archaeologists will present their findings to peers and may follow up with targeted digs.

Aventicum's rise and two-thousand-year fade

The city under the fields was founded roughly two thousand years ago, after Julius Caesar defeated the local tribes and the Romans established a capital for the territory they called Helvetia. Aventicum thrived under Roman rule, growing into a genuine urban center with baths, temples and a street grid. Then, as Germanic incursions increased from the third century onward, the city gradually faded, and the small town of Avenches eventually grew over part of it.

That long fade is why so much was still hidden. Many of the newly mapped traces sit in areas of the ancient city that had not previously been systematically dug, which means the drone survey has effectively redrawn the map of a provincial Roman capital with barely a shovelful of earth moved. Similar buried remains have surfaced elsewhere in Switzerland and Europe during recent dry spells, but isolated finds without dedicated researchers are far harder to interpret, which makes the Avenches team's systematic daily survey unusual.

A record season for accidental archaeology

The Swiss discovery is part of a wider pattern: extreme weather keeps doing archaeology's scouting work. The same heatwaves that exposed Aventicum also laid bare Second World War wrecks on dried riverbeds. And September 2026 has been an unusually busy month underground in general. At Göbeklitepe in southeastern Türkiye, archaeologists uncovered the first two intact burial contexts at the eleven-thousand-year-old site, a find that may solve a decades-old mystery about hundreds of scattered human bones. A study published September 22, 2026 in the journal PLOS One proposes that erosion and landslides carried remains from dwellings on higher ground into the monumental structures below, rather than all of them being deliberately placed there, according to HeritageDaily.

Elsewhere, roadworks in Georgia's capital Tbilisi unearthed a rare tenth-century pottery cache, and a hoard of Roman silver coins turned up on the Swedish island of Gotland. For readers, the takeaway is that climate extremes are redrawing ancient maps faster than traditional excavation alone, and non-invasive techniques like drone survey let researchers capture sites before the next rain washes the evidence away. What happens next at Avenches is the slow part: peer review, and possibly the targeted digs that turn parch marks into museum pieces. Follow our The Old World coverage for more, and see how young people are pushing climate action through the courts in our report on the Canadian teens' climate lawsuit.