In 2011, hikers in the snowy mountains of central Norway came across a 1700-year-old wool tunic, likely belonging to a Roman-era hypothermia victim. As ice in the region has continued to melt, researchers have made hundreds of additional finds. Now, archaeologists have made their biggest discovery yet: a lost Viking trade route that may have been used for hundreds of years to ferry everything from butter to reindeer antlers to far-flung European markets.