In 1961, Oxford archaeologists uncovered a pit at the site of Gen. Gnaeus Julius Agricola's headquarters at Inchtuthil, the site of a Roman legionary fortress, in Scotland. Unsavory Caledonians had made his troops' position untenable.

STUFF MATTERS: The Strange Stories of the Marvellous Materials that Shape Our Man-Made World, by Mark Miodownik Viking, 2013, 272 pp., £18.99 (hardcover)

So the Romans decided to quit their empire's northernmost outpost, though not before going to extraordinary efforts to ensure they left nothing behind that could aid their enemies.