Scattered all across Britain are ancient monuments that are thousands of years old.
They tell of a rich Neolithic period, in which Britons experimented with compelling and cutting-edge engineering techniques.
Why they built many of the structures they did we still don’t know, with various theories floated from giant burial grounds to ways to observe the night sky.
Silbury Hill is one of these monuments, a great hulking structure part of the wider Avebury Neolithic site.
A UNESCO World Heritage Site, Silbury Hill is perhaps the most perplexing of all of Britain’s prehistoric monuments and one that isn’t any closer to being cracked than when it was discovered in 1776.
The largest artificial mound in Europe, “mysterious Silbury Hill”, as English Heritage describes it, compares in height and volume to the roughly contemporary Egyptian pyramids.
Historians believe it was likely completed at some time around 2400 BC. While many similar structures contain burials, Silbury Hill, as far as we know, contains no burial.
The structure itself must have served some important purpose, but what that purpose is is unknown.
It is composed mainly of chalk and clay taken from the surrounding area, and stands at 40 metres, or 131 feet high, covering a sizeable five acres.
Between 2400 and 2300 BC, Silbury Hill was constructed in several stages and displayed considerable technological skill and prolonged control over labour and resources.
For ancient Britons to continuously build the monument over some time and pass construction knowledge and a sense of meaning through generations of people, Silbury Hill would have been seriously important.
Archaeologists calculate that it took 18 million person-hours, equivalent to 500 people working for 15 years.
They deposited and shaped 248,000 cubic metres of earth and fill to create the mound, erecting it in a way that its weight and dimensions were distributed so it didn’t collapse.
Euan Mackie, who was a celebrated archaeologist, argued that no primitive late Neolithic tribal structure we ordinarily associate with the time could have sustained the Silbury Hill projects as well as much of that found among the Averbury heritage site.
Interestingly, he believes that some sort of authoritarian theocratic power elite with broad-ranging control across southern Britain operated, with the monument and others like it built with fierce intention.
The base of the hill is circular and 548 feet in diameter, with the present-day summit completely flat.
It is believed that the summit would originally have been curved, but it was flattened in the Middle Ages to provide a base for a building, perhaps with a defensive purpose.
The site was first illustrated by the seventeenth-century antiquarian John Aubrey whose accompanying notes were published between 1680 and 1682.
Antiquarian William Stukeley later wrote that a skeleton and a bridle had been found during tree planting at the hill’s base, though it is likely that the skeleton came from a later burial than the Neolithic period.
In mid 19th century, archaeologists excavated the east side of the hill to investigate whether a Roman road lay beneath it, but no traces were found.
It wasn’t until 1968 that serious archaeological work was undertaken to determine where and when Silbury Hill came from, which was broadcast on the BBC.
Vital clues were found, like the presence of winged ants inside the monument, which hinted that construction of it had begun in August.
Work in this century has furthered understanding of the fort, like the discovery of a Roman village at its foot in 2007.
Last month, heavy rains saw a moat form around Silbury Hill’s base, and while heavy rains have caused problems at the site in the past, English Heritage said the lake that forms seasonally around Silbury Hill is not a problem and drains away naturally.
