It looked to be a routine excavation of what was thought to be a burial mound. But beneath the mound, archaeologists from the Norwegian University of Science and Technology’s Museum of Natural History and Archaeology found something more: unusual Bronze Age petroglyphs.
”We believe these are very special in a Norwegian context,” says museum researcher and project manager Anne Haug.

The in Stjordal, just north of Trondheim, was necessitated by the expansion of a gravel pit. Given that project didn’t anticipate that the dig would be very complicated, the museum researchers dedicated just three weeks to the effort.

http://pda.physorg.com/news/2011-01-norwegian-petroglyphs-beneath-burial-mounds.html