Typically rainy Scotland is in the middle of an unusually dry summer—and local archaeologists are taking advantage of it. As the BBC reports, the drought has revealed ancient sites, including Roman camps and Iron Age graves, that have been hidden by farm soil for years.

Historic Environment Scotland has been conducting aerial surveys of the country's landscape since the 1930s, but it's in seasons like this, when the crops recede during dry weather, that the buried remains of ancient structures are easiest to spot. Conditions this summer have been the best since 1976 for documenting archaeological sites from the sky.

Historic Environment Scotland

The crescent-shaped crop mark in the photo above indicates a souterrain, or underground passageway, that was built in the Scottish Borders during the Iron Age. The surveyors also found remains of a Roman temporary camp, marked by straight lines in the landscape, built in modern-day Lyne—an area south of Edinburgh already known to have housed a complex of Roman camps and forts.

Historic Environment Scotland

In the image below you'll see four small ditches—three circles and one square—that were likely used as burial sites during the Iron Age. When crops are planted over an ancient ditch, they have more water and nutrients to feed on, which helps them grow taller and greener. Such crops are especially visible during a drought when the surrounding vegetation is sparse and brown.

Historic Environment Scotland

Historic Environment Scotland has a team of aerial surveyors trained to spot the clues: To date, they've discovered more than 9000 archaeological sites from the air. HSE plans to continue scoping out new areas of interest as long as the dry spell lasts.

It's not just in Scotland that long-hidden settlements are coming to light: similar aerial surveys in Wales are finding them too.

[h/t BBC]