Scientists discovered the exact location of the quarries where dozens of Stonehenge's massive stones came from, a study released Tuesday said.

In addition to pinpointing the location of the quarries – in western Wales, about 180 miles away from Stonehenge – archaeologists said they know how and when the stones were quarried.

"What's really exciting about these discoveries is that they take us a step closer to unlocking Stonehenge's greatest mystery – why its stones came from so far away," said study lead author Mike Parker Pearson of University College London. "Every other Neolithic monument in Europe was built of megaliths brought from no more than 10 miles away."

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The answer? The stones were quarried so far away from Stonehenge because they were relatively "easy" to remove, Pearson theorized, since they were natural vertical pillars. Using wood mallets, quarry workers only had to bash wedges into the ready-made joints between the pillars to break them apart, according to the study.

The 2-ton stones were lowered onto wooden sledges and dragged or carried to their new location in present-day England.

The quarried stones are the interior rocks of Stonehenge, separate from the larger outer ring.

Unlike stone quarries in ancient Egypt, where obelisks were carved out of solid rock, the Welsh quarries were easier to exploit, the study says.

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Though geologists have long known that many of Stonehenge's smaller stones came from present-day Wales, the new study identifies the exact locations of two of these quarries: the Preseli Hills in Pembrokeshire, west Wales.

The study suggests the stones were quarried around roughly 3000 B.C., based on pieces of charcoal found at the site, which were dated to that era.

The stones at Stonehenge may have been part of a circle of stones in Wales, which might have been disassembled and reassembled at its present location.

Stonehenge, one of the most impressive prehistoric megalithic monuments on Earth, is a World Heritage site known for its alignment with the movements of the sun. Thousands of people travel there each year to mark the solstices in summer and winter.

Built in several phases from 2900 B.C. to 1650 B.C., the stones have figured in numerous debates, both scholarly and whimsical, over their origins.

Tuesday's study was published in the peer-reviewed archaeology journal Antiquity.