The Watlington White Mark

https://commons.wikimedia.org/wiki/File:Watlington_whitemark.jpg

In 1764 Oxfordshire squire Edward Horne decided that the parish church of St Leonard on Watlington Hill would look more impressive with a spire. So he gave it one: By cutting a narrow mark 270 feet long into the chalk soil beyond the building, he was able to perch a foreshortened triangle atop the church when it was viewed in perspective from his house. Local residents maintain the mark to this day.