Ancient settlements, long buried and forgotten throughout the Welsh countryside, are suddenly placing themselves back on the map –– and all thanks to the scorching heat wave gripping the Northern Hemisphere.

According to the Royal Commission on the Ancient and Historical Monuments of Wales, record-breaking temperatures that have scorched fields and farmland across the region have also produced a phenomenon called "cropmarks." These tell-tale signs of ancient monuments and settlements were once fortification ditches, long eroded or plowed over, but still capable of holding water and nutrients. As a result, plants growing in these hidden manmade oases remain green during periods of extreme drought even as the surrounding vegetation wilts and browns.

As shown below, the best way to spot these fascinating signs of history are from the air.

Newly discovered cropmarks of a prehistoric or Roman farm near Langstone, Newport, South Wales. Newly discovered cropmarks of a prehistoric or Roman farm near Langstone, Newport in South Wales. (Photo: Royal Commission on the Ancient and Historical Monuments of Wales)

Dr. Toby Driver, a senior aerial archeologist for the Royal Commission, has spent the last several weeks documenting known and newly discovered sites of interest. So far, dozens have appeared over the parched Wales landscape.

"I've not seen conditions like this since I took over the archaeological flying at the Royal Commission in 1997," he told Wales Online. "So much new archaeology is showing — it is incredible."

The possible remains of a Roman villa in Chester-Gwent, South Wales. The possible remains of a Roman villa in Chester-Gwent, South Wales. (Photo: Royal Commission on the Ancient and Historical Monuments of Wales)

As quickly as the sites appeared, however, it only takes a break in the dry spell to quickly mask them under a sea of green. As such, the Royal Commission is in a race against time to document as many of these cropmarks as possible.

"With the drought expected to last at least another two weeks Toby will be surveying right across north and south Wales in a light aircraft to permanently record these discoveries for the National Monuments Record of Wales, before thunderstorms and rain wash away the markings until the next dry summer," the group stated in a release.

The buried ramparts of Cross Oak Hillfort, Talybont on Usk, showing as cropmarks The buried ramparts of Cross Oak Hillfort, Talybont on Usk, is revealed in these cropmarks. (Photo: Royal Commission on the Ancient and Historical Monuments of Wales)

According to Driver, while excavations of the sites are not currently planned, the newly discovered sites will keep the team busy for some time to come.

"The urgent work in the air now will lead to months of research in the office in the winter months to map and record all the sites which have been seen, and reveal their true significance," he added.

settlement ruins What appears to be the outline of an ancient building appeared in a field in Ireland. (Photo: Mythical Ireland)

Another settlement was also spotted recently in Ireland. Photographer Anthony Murphy snapped this aerial image of a circular pattern in a field located in Newgrange.

"They look like giant henges or enclosures," Murphy said on his Facebook page. "Have a look at these very exciting photographs. If these turn out to be substantial discoveries, then I would be nothing short of utterly elated, chuffed and excited. We're already discussing them with an archaeologist and to say he's very excited is a huge understatement!"

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Heat wave in U.K., Ireland reveals ancient settlements
Extreme dry conditions have aerial archeologists racing against time to document an unusual marker of forgotten monuments.