Answer: Oil Jars

Outside of Rome is a scenic hill, one of the many that surround the city, known as Monte Testaccio. To an observer in the 21st century, there’s nothing particularly unusual about the enormous mound. It’s covered in lush vegetation and trees, overlooks the River Tiber, and makes for a lovely spot to hike and have a picnic lunch if you’re so inclined.

Without getting your hands dirty and doing some serious digging, however, you’d never know that the hill is man made and your picnic lunch is taking place on one of the largest waste mounds of the ancient world.

Beneath the soil of Monte Testaccio lies the remains of an astounding 53 million olive oil jars, or amphorae, that were deposited there during a four hundred year span beginning in approximately the 1st century BC. The mound is a testament to the enormous appetite the Romans had for olive oil. The demand for olive oil was so high that it was imported from far reaches of the empire to Rome in large clay jars, decanted at the nearby port, and then the clay vessels were disposed of at Monte Testaccio. Unlike other vessels used by the Romans, the large globular oil containers were difficult to recycle and a system was put in place for disposing of them.

The disposal was highly organized and the mound was carefully planned. Archaeologists excavating the site have long marveled at how organized the structure of the discarded pots and their shards is; the layers are carefully arranged in stable patterns and sprinkled with lime (presumably to mask the smell of the rancid oil). It is estimated that the quantity of vessels in the mound represents an olive oil import of roughly 1.6 billion gallons.