Archaeologists have discovered a secret sister monument to Stonehenge that might have served as a 'prototype' for the famous stones.

This ancient site is just three miles away from Stonehenge itself, located in the village of Bulford, Wiltshire.

Consisting of two wooden poles placed 400 feet (120 metres) apart, this long–lost monument might appear rather basic at first glance.

However, scientists say the poles would have formed a perfect line pointing to the rising sun during the summer solstice and the setting sun on the winter solstice.

In fact, reconstructions of the ancient sky and landscape show that the deceptively simple structure was built to align with the solstice within one degree of accuracy.

More impressively, archaeologists have dated this structure back to around 5,000 years ago.

That predates the monument we see at Stonehenge by 500 years, making this one of the very oldest examples of a structure built to align with the sun in the British Isles.

Dr Fabio Silva, an archaeologist from Stone x Sky and the Skyscape Academy, says: 'Rather than marking the beginning of a story, Stonehenge now more clearly appears to have emerged from traditions and practices with much deeper roots in this landscape.'

Since any wood has long since rotted away, almost nothing is left of the Bulford ritual site today besides the pits where the poles once stood.

However, these scant clues are already giving archaeologists a fascinating glimpse into Britain's ancient past.

The site of the Bulford poles was first uncovered in 2015, when archaeologists found a network of 48 pits dated to around 2950 BC.

Excavations found that these pits were filled with the remains of pottery, animal bones, flint tools, and charcoal.

It was clear that large numbers of people gathered in this area over a relatively short period of time, but archaeologists weren't sure what they were gathering for.

Now, the alignment of the poles suggests that people likely gathered by this simple monument to celebrate the solstices before more complex, permanent structures could be built.

While Stonehenge and the Bulford site have different layouts, this shows that the 'technology' of tracing the sun's alignment on the horizon existed long before the more famous structure was built.

In fact, the researchers suggest that Bulford and Stonehenge might have had an even closer connection.

Phil Harding, Archaeologist at Wessex Archaeology and former host of Time Team, told the Daily Mail that some of the people who built Bulford might have been buried in the 'Aubrey Holes' at Stonehenge, where cremated remains have been found.

He said: 'Even if the people who visited Bulford are not buried at Stonehenge, there is every possibility that the people who visited Bulford may have also visited Stonehenge, and may even have been involved in the construction of Stonehenge.'

The pits and Bulford date back to almost the exact same period that the first simple earthworks were being put up at the site of Stonehenge.

Mr Harding even suggests that a similar pole structure might have been part of the earliest phases of Stonehenge, but later developments would have erased any trace of the pits.

'These people lived in a world that was controlled by the heavens, by climate, by natural circumstances,' he says.

'They cared about their world and the natural processes of the sun... this [the solstice] must have been such a major event in their lifetimes.'

This discovery also helps to solve the mystery of an extremely rare disc–shaped knife found in one of the pits.

Mr Harding found this round knife buried vertically in a pit located almost exactly on the line of the solstice.

'It's an absolutely exquisite object,' Mr Harding says.

'That is a difficult craft to exercise to that level of perfection. It's almost inconceivable that you would just throw it away.'

Now, Mr Harding says the disc could have been a symbolic reference to the disk of the sun, deliberately placed in a sort of 'viewing station' for the solstice.

Archaeologists still debate exactly what Stonehenge and similar sites, like the Bulford poles, would have been used for.

However, their alignment with the solstice is a strong indication that they had a spiritual or religious function besides simple timekeeping.

Dr Matt Leivers, Senior Research Manager at Wessex Archaeology, says: 'When we talk about the solstice, we're talking about religion. About how prehistoric peoples understood the cosmos, the world, and their place in it.

'What we see at Bulford, and later at Stonehenge, is a way of celebrating and marking the passage of time, but it's also about making sure the world keeps working as it should.' 

'It's likely their way of saying to their deities, please keep us in mind, keep us warm and safe. It's a religious event. That's why it's so important'