Researchers at the University of Reading in the UK investigated the site of a Neolithic long barrow burial mound in a place known as Cat's Brain - the first to be fully investigated in Wiltshire in half a century.
The monument, which predates nearby Marden Henge by over 1,000 years, may contain human remains buried there in around 3600 BC, researchers said.
The monument was first spotted by aerial photography and followed up by geophysical survey imagery, they said.
"Opportunities to fully investigate long barrows are virtually unknown in recent times, and this represents a fantastic chance to carefully excavate one using the very latest techniques and technology," said Jim Leary, Director of the Archaeology Field School at Reading.
"Discovering the buried remains of what could be the ancestors of those who lived around Stonehenge would be the cherry on the cake of an amazing project," Mr Leary said.
The Cat's Brain long barrow, found in the middle of a farmer's field halfway between the iconic prehistoric monuments of Avebury and Stonehenge, consists of two ditches flanking what appears to be a central building.
This may have been covered with a mound made of the earth dug from the ditches, but has been ploughed flat over many centuries.
The last long barrow to be fully investigated in Wiltshire was in the 1960s.
The team will now conclude the three-year project by excavating the archaeological remains and recover artefacts, bones, and other environmental evidence, which will be analysed.
This analysis will provide crucial evidence for the people and society in Britain during this remote period.
In addition to the Cat's Brain long barrow site, the University of Reading's Archaeology Field School is working at Marden henge, the largest henge in the country, built around 2400 BC, also within the Vale of Pewsey.
"This incredible discovery of one of the UK's first monuments offers a rare glimpse into this important period in history. We are setting foot inside a significant building that has lain forgotten and hidden for thousands of years," said Amanda Clarke, co-director of the Archaeology Field School.