Stonehenge may have been a place for sun worship long before the iconic stones were erected more than 5,000 years ago, according to archaeologists who are carrying out the biggest-ever virtual excavation.
Using noninvasive technologies such as ground-penetrating radar and geophysical imaging, a team from the University of Birmingham's IBM Visual and Spatial Technology Centre, known as VISTA, and the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology in Vienna, discovered evidence of two huge pits positioned on a celestial alignment at Stonehenge.
Measuring more than 16 feet across and at least 3 feet deep, the pits lie within the Cursus, a large enclosure north of Stonehenge, which predates the prehistoric monument by up to 500 years.
"This is the first time we have seen anything quite like this at Stonehenge," said project leader Vince Gaffney, an archaeologist from the University of Birmingham.
"When viewed from the Heel Stone, a rather enigmatic stone which stands just outside the entrance to Stonehenge, the pits effectively mark the raising and setting of the sun at midsummer days," he explained.
According to the archaeologists, the pits may have contained tall stones, wooden posts or even fires to mark the sun rising and setting. Most likely, they defined a processional route used to celebrate the passage of the sun across the sky at the summer solstice.
"It is possible that processions within the Cursus moved from the eastern pit at sunrise, continuing eastwards along the Cursus and, following the path of the sun overhead, perhaps back to the west, reaching the western pit at sunset to mark the longest day of the year," said Gaffney.
The hypothesis gained more weight when the researchers measured the walking distance between the two pits.
They discovered that the procession would reach exactly halfway at midday, when the sun would be directly on top of Stonehenge.
"This is more than just a coincidence, indicating that the exact length of the Cursus and the positioning of the pits are of significance," said Henry Chapman, senior lecturer in archaeology and visualization at the University of Birmingham.
According to the researchers, the presence of the pits within the Cursus suggest that the Stonehenge area, which features England's densest complex of Neolithic and Bronze Age monuments, was already sacred before construction work began to build the enigmatic stone circle.
"Even though Stonehenge was ultimately the most important monument in the landscape, it may at times not have been the only, or most important, ritual focus," said Gaffney.
"The area of Stonehenge may have become significant as a sacred site at a much earlier date. Other activities were carried out at other ceremonial sites only a short distance away," he continued.
The researchers have already found a henge-like monument, several other small monuments, and a new horseshoe arrangement of large pits northeast of Stonehenge, which may have also contained posts.
They believe that these structures functioned as minor shrines, perhaps serving specific communities visiting the ceremonial center.
The team is confident that the project will produce new discoveries soon.
"Our knowledge of the ancient landscapes that once existed around Stonehenge is growing dramatically as we examine the new geophysical survey results," said Paul Garwood, a lecturer in prehistory at the University of Birmingham.
"We can see in rich detail not only new monuments but entire landscapes of past human activity, over thousands of years, preserved in subsurface features such as pits and ditches."