for National Geographic News
Tomb engravings dating back 6,000 years are among the latest discoveries unearthed on the route of a controversial highway under construction in Ireland.
The historic site, at Lismullin in County Meath, was handed over to road builders last month, just weeks after the Stone Age art was found inside a medieval bunker.
The engravings have been removed to allow construction of the highway to proceed.
The new find follows the discovery last spring of a prehistoric open-air temple nearby, causing construction along the 37-mile-long (60-kilometer-long) M3 highway northwest of Dublin to be temporarily suspended (see map).
The timber ceremonial enclosure was found just 1.25 miles (2 kilometers) from the Hill of Tara, once the seat of power of ancient Celtic kings.
The latest excavations at Lismullin revealed part of a large stone monument, or megalith, decorated with engravings dating to the Late Stone Age, according to archaeologists from Ireland's National Roads Authority (NRA).
Discovered some 165 feet (50 meters) from the temple's enclosure, the stone features a series of zigzags, concentric circles, and arcs.
"It's classic megalithic art," said Mary Deevy, NRA's chief archaeologist.
The engravings are similar to those that decorate other burial chambers in the region known as passage tombs, Deevy noted.
"We've only got half a boulder, but we think originally it was probably a curbstone from a passage tomb," she said.
The stone would have formed a wall that kept the burial mound together, with the artwork displayed on the outer surface, Deevy said.
What the motifs symbolized remains a mystery, the archaeologist added.
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