Stonehenge may have been surrounded by a "Stonehedge" that blocked onlookers from seeing secret rituals, according to a new study.
Evidence for two encircling hedges—possibly thorn bushes—planted some 3,600 years ago was uncovered during a survey of the site by English Heritage, the government agency responsible for maintaining the monument in southern England.
The idea that Stonehedge was a shield against prying eyes isn’t yet firmly rooted, but it's archaeologists' leading theory. For instance the newfound banks are too low and unsubstantial to have had a defensive role.
"The best [theory] we can come up with is some sort of hedge bank," said English Heritage archaeologist David Field, whose team discovered the two landscape features in April 2009.
"We think they served as some sort of screen to filter access to the center [of Stonehenge]." (See Stonehenge pictures.)
The shallow earthworks—each runs inside a ring of known Bronze Age pits—are just visible to an expert eye, "but you need to get down on your hands and knees" to see them, Field added.
The archaeologists didn't find any physical evidence of vegetation, but the shallow features resemble former hedge banks that are seen around formerly hedged fields.
While there’s no firm evidence for a British prehistoric landscape-gardening tradition, there's evidence for tree cultivation at the time Stonehenge was in use.
"It seems standard-size trees were being cultivated and looked after in order to provide straight, telegraph-pole-like features for the construction of palisades [fences of defensive stakes] and so on," Field said.
With that in mind, Stonehedge's "vegetation screens are quite feasible," Field said. "Something like thorn bushes … or small trees."
Past archaeological investigations at Stonehenge have tended to focus chiefly on the stones themselves, he noted.
"To date nobody has really considered the vegetation around the stones."
The latest finds, reported in the March/April edition of British Archaeology magazine, come "completely out of the blue," according to editor Mike Pitts, an archaeologist and Stonehenge expert.
The magazine, a publication of the Council for British Archaeology, often publishes archaeologist-written reports on new finds.
While Pitts thinks the hedge theory is "a perfectly reasonable explanation … there have been no excavations of these features, so until that happens we won’t really know what’s going on."
The April 2009 landscape survey employed advanced equipment, such as high-resolution surface lasers, to discern shapes invisible to the human eye.
"Believe it or not, it's the first earthworks survey of the monument since 1919," Pitts added. "Unsurprisingly, all sorts of things were found."
Those include a flattened mound near the center of Stonehenge, which may be a burial. The Stonehenge area is littered with prehistoric burial mounds, and the monument itself likely served first and foremost as a cemetery, experts say.
Partially concealed by fallen stones, the forgotten mound had been previously recorded in 18th- and 19th-century watercolor paintings.
"There’s a good chance it's prehistoric," said English Heritage's Field.
The suspected burial mound possibly dates to the earliest phases of the monument, as early as 5,000 years ago, Field said.
If the mound was built first, "it may be that this was the focus around which Stonehenge developed."