If you happen to be flying over County Donegal in the republic of Ireland, you may be astonished to see a beautiful arrangement of conifer trees in the shape of a Celtic cross growing on the ground below.

"It's not just cutting patterns in your back garden," Gareth Austin, a gardening columnist for the Donegal Daily said. "This is horticultural engineering – we will be appreciating this for up to the next 70 years."

To pull off the beautiful design, measuring 330 feet long by 210 feet wide, two different species of trees were planted. Every autumn, the Celtic trees (likely composed of Eastern white pine) change their hue, while the surrounding species retains its dark green. The display went viral this fall after a particularly dry stretch of months made the colors contrast sharply. Airline passengers couldn't resist posting to social media about the mysterious cross. And as shown in the video above, drone pilots quickly followed.

When a reporter for UTV Northern Ireland went to investigate, he discovered that the creative planting was the work of Irish forester Liam Emmery. Sadly, Emmery passed away six years ago at the age of 51. Until this year's dramatic display, his family had completely forgotten about the legacy he had planted on the hill behind their home.

"If he was here, we would have all heard about it because he would have been so proud," Liam's wife, Norma Emmery, told The Irish Post. "He just loved things to be perfect. And I think the Celtic Cross is perfect for him."