The world's largest ancient Roman rubbish dump is revealing intriguing details about the extent and sophistication of trade in the Mediterranean 2,000 years ago. Monte Testaccio is an artificial hill in the centre of Rome that is made up of an estimated 25 million shards of broken amphorae, many from as far afield as Spain and North Africa. The amphorae, containing wine and olive oil, were broken up and dumped on the spoil heap after being unloaded from a nearby port on the River Tiber. They could not be reused because wine and oil residue seeped into the clay, turning...