Anthony Murphy and Ken Williams were flying a drone over the Boyne Valley in Ireland on Tuesday afternoon when they spotted something interesting. Their video depicts what appears to be the footprint of nearly 50 large wood formations. Oriented much like Stonehenge, the discovery is in line with other large monuments in the area known to have been constructed around 5,000 years ago.

Murphy said he has flown his drone on numerous occasions over the same parcel of land, but this was the first time he saw the site, which looks like a giant crop circle.

“The weather is absolutely critical to the discovery of this monument,” Murphy said, according to the Irish Times. “I have flown a drone over the Boyne Valley regularly and have never seen this.”

The newly discovered ancient site is close to the 5,000-year-old Newgrange neolithic passage tomb.

Murphy said he and Williams notified the Department of Culture, Heritage and the Gaeltacht. It has yet to decide what to do next about the curious find, the Irish Times reports:

The National Monuments Service will now be doing some further technical work to help determine the nature of the site, but from the drone images visible on social media, it is a very significant find which fits within the knowledge of large prehistoric ritual enclosures and associated ritual landscapes as at Bru na Boinne.

According to Met Eireann, Ireland’s meteorological service, northeast Ireland has been in drought for around a month, following a very wet spring. No rain has fallen so far in July in Dunsany, the observing site 10 miles south-southwest of Newgrange where the discovery was made.

Last month, only 1.18 centimeters came down, and during May, a mere 3.32 centimeters. In just the past two months, the region has been running about 70 percent below where it should be. Couple this with warmer-than-normal temperatures, and it’s easy to see why all grass and vegetation has largely browned and dried out.

One characteristic of the large structures is their tendency to change the composition of the surrounding soil. The wood inevitably decayed and fertilized the soil in the process. The nutrients from the wood are great for vegetation and even help the soil retain more water, which is why these areas are greener than their surroundings. The region got plenty of rain in the spring, and the super-fertile soil is hanging on to that moisture.

If the remarkable find hadn’t been caught when it was, we might not have known about it for many years to come. The stretch of hot and dry weather facing the region is about to come to an end as remnants of Hurricane Chris ride the jet stream toward Ireland and Britain. Weather Advisories — “status yellow” — have been issued for the resulting rainfall approaching in the days ahead.

Correction: An earlier version of this story said the newly-discovered henge site was originally made of stone. It was actually made of wood.