It started with an 1,800-year-old shirt. Archaeologist Lars Holger Pilø had watched his colleagues discover the ancient wool tunic that had emerged from a melting ice patch on Lomseggen, a mountain in southern Norway. Now Pilø wondered what else was out there. As the rest of the team packed up the precious find, he and another archaeologist wandered away from the group, tracing the edge of the melting ice shrouded in mountain fog.

As he peered into the gloom, Pilø soon realized he was looking at a field of objects that hadn’t seen the light of day for hundreds of years. Broken sleds, tools, and other traces of daily life going back nearly 2,000 years lay strewn across the surface of