When diggers moved on to a 10.5-hectare valley near the source of the River Avon on Monday (June 28 2010), they were entering uncharted territory.
Marden Henge may lie in a Neolithic Nirvana, with Stonehenge to the south and Avebury to the north, but this huge field – decimated by years of ploughing and erosion – is the new focus for experts who believe "significant" prehistoric rituals or ceremonies may have been held there.
"We have always assumed there was activity around here," admits English Heritage archaeologist Jim Leary. "Now it's a case of testing it to see if that's the case."
Part of a long term project in the surrounding vale, this latest quest was launched after aerial photographs suggested the Henge was a particularly rich potential point of investigation, with a mysterious circular feature in the southern half surrounded by a bank and gullies.
The press have seized on the excavation because of the size of the site, which dwarfs Stonehenge, although the investigators say it is probably more comparable with Silbury Hill, the nearby mound which once towered over a Roman village.
"We're digging for six weeks," explains Leary, describing a 15-man team working with generators and wheelbarrows full of tools.
"We'll dig as much as we can, collect the finds, collect the samples and then send them off for carbon dating and environmental assessments in the labs. We'll find everything from pollen to snail shells. It's a pretty long process."
For Leary, the wait for the shroud of intrigue to lift is a more stirring prospect than the hard work taking place now.
"They'll carry out all sorts of tests on them," he adds. "That is by far and away the most exciting bit of the excavation."