Ancient underground complex sat beneath Stonehenge

The massive hunks of granite that make up Stonehenge are just part of a much larger puzzle. As new research reveals, Stonehenge is what remains of was once a vast complex of burial mounds and shrines -- some above the earth, much more buried beneath.

As part of the Hidden Landscapes Project, researchers from the University of Birmingham teamed up with an international team of archeologists to survey the grounds surrounding Stonehenge. The scientists spent four years mapping what was once a massive complex of pits, monuments and all sorts of earthworks.

Using ground-penetrating radar and other tools, the researchers were able to locate 17 previously unknown ritual monuments, as well as scan and map other known artifacts and monuments without disturbing the grounds around Stonehenge -- a UNESCO World Heritage Site situated some 80 miles southwest of London.

Among the unique findings was the discovery that during Stonehenge's earliest stage, the circle of stones was flanked on either side by a row of 60 10-foot-tall posts or stones. Researchers also found that a vast of array of burial pits appear to form astronomic alignments. As well, a number of newly-discovered burial mounds offer clues to the civilizations that once populated the grounds of Stonehenge -- people from the Bronze Age, Iron Age and Roman settlements.

"The Stonehenge Hidden Landscapes Project is unique at a global level," said project leader Professor Vincent Gaffney. "Not only has it revolutionized how archaeologists use new technologies to interpret the past, it has transformed how we understand Stonehenge and its landscape."

"Despite Stonehenge being the most iconic of all prehistoric monuments and occupying one of the richest archaeological landscapes in the world, much of this landscape in effect remains terra incognita," Gaffney added. "This project has revealed that the area around Stonehenge is teeming with previously unseen archaeology and that the application of new technology can transform how archaeologists and the wider public understand one of the best-studied landscapes on Earth."