A fun story about this giant chalk horse carved into the side of a hill in Oxfordshire, England can be read here. What's new to me in that story is the dating of the football-field-sized pictogram as 3000 years old. The dating was made possible by a technique called optical stimulated luminescence:
“It was older than I’d been expecting,” Miles remembers. “We already knew it must be ancient, because it’s mentioned in the 12th-century manuscript The Wonders of Britain, so it was obviously old then. And the abstract shape of the horse is very similar to horses on ancient British coins just over 2,000 years old. But our dating showed it was even older than that. It came out as the beginning of the Iron Age, perhaps even the end of the Bronze Age, nearly 3,000 years ago.”
What's most fascinating about the pictogram is that it has required regular upkeep all through its history and that it has received it and still does:
From the start the horse would have required regular upkeep to stay visible. It might seem strange that the horse’s creators chose such an unstable form for their monument, but archaeologists believe this could have been intentional. A chalk hill figure requires a social group to maintain it, and it could be that today’s cleaning is an echo of an early ritual gathering that was part of the horse’s original function.