Rome’s Oil Mountain: The Story of Monte Testaccio

Marcus Valerius

If you walk down past the Aventine hill on a hot morning, right down to the riverfront at the Emporium, the the first thing that hits you is not the sight of Rome. It is the smell. It is a thick, heavy coat of rancid olive oil hanging right in the summer air. Out on the Tiber, those flat bottomed river barges from Ostia are sitting low in the muddy water, bumped right up against the quays. Dockworkers are swarming over them, lifting off these massive, round bellied pottery jars. They are Spanish oil jars, what the scholars call Dressel twenty amphorae, each one holding about seventy liters of pure oil from the province of Baetica.

Marcus Valerius

Now, you would think once they unload those jars outside the grand state warehouses at the Horrea Galbae, they would decant the oil into big storage tubs and send the jars back, or or maybe crush them up for building work. But no. If you follow the line of pack mules, you see them hauling those empty clay jars straight up what looks like a mountain. A man made mountain right here in the city, Monte Testaccio. Laborers stand up on stepped terraces, seventy feet up in the air, smashing the pots with heavy mallets. And as they break them, another worker sweeps in with a shovel, dusting the fresh reddish sherds with white lime powder. I asked one of them once why they do it, and he scoffed at me. He said if you do not dust the shattered clay with lime, the August heat rots the oil soaked into the pottery, and the stench would choke out half the Aventine by noon.

Marcus Valerius

It turns out there is a very clever engineering secret behind why we dump millions of pots right here instead of recycling them. See, with wine jars or grain amphorae, we smash the clean clay into tiny chips and mix it into mortar. We call it opus signinum, and it makes our floors and cistern walls tough as iron. But you cannot do that with oil jars. That oil soaks deep into the porous baked clay, and if you mix oily clay with hot lime mortar, well, chemistry happens. The oil reacts with the lime and turns into soap. Yes, real slippery soap right inside your building mortar. If you tried to build a bathhouse vault or an aqueduct wall with broken oil jars, the concrete would crumble into greasy sludge. So the state engineers had to build a dedicated disposal mountain instead.

Marcus Valerius

For years, I tell you, I thought Monte Testaccio was just a high grassy hill at the edge of the river district. I used to see boys running up the slope to fly kites. Then one afternoon, a few summers back, I climbed up the eastern side to catch a breeze, stepped off the dirt path onto a crumbling terrace, and crunch. My sandals slid right through a layer of baked terra-cotta. I looked down, scraped away a handful of dry weeds, and realized the entire ground beneath my feet, for fifty or sixty feet straight down, was nothing but broken handles, rims, and pot bellies. I was standing right on top of fifty million shattered pots. It takes a city of a million hungry bellies to pile up a mountain out of its garbage.

Marcus Valerius

Down at the docks, the noise is deafening. Shouting porters, timber gangplanks creaking under load, and right in the middle of it all sits a port notary, a scriba, perched on a wooden stool with his wooden tablet and reed pen. I stood beside him for a moment while two sweat soaked porters wrestled a huge seventy liter jar off a barge. The notary leaned over, squinting at the neck of the jar, and read out the black ink inscriptions painted right on the clay. In the trade, we call those markings tituli picti. The notary read off the empty weight of the vessel itself, what we call the tare weight, then the exact net weight of the Baetican olive oil inside, and then the name of the merchant partnership that shipped it across the sea.

Marcus Valerius

It is an unbelievable piece of imperial bureaucracy. Under our Emperor Trajan, the office of the praefectus annonae, the official in charge of the city food supply, keeps a grip on this trade that is tight as a vice. Before a single drop of oil leaves Spain, five separate ink notations are painted onto the shoulder of that jar. The estate owner signs, the local weighers sign, the district inspector stamps his mark, all to guarantee that no greedy shipping captain siphons off the emperor's oil along the way or waters it down to stretch his profit. Every jar is tracked from the olive grove in southern Spain straight to the bread and oil dole here in Rome.

Marcus Valerius

While I was standing there, a dock porter carrying a heavy linen sling sat down on a crate to catch his breath. He pointed out a deep stamp pressed into the clay handle of a broken jar nearby. It was the mark of the pottery workshop where the jar was fired. He told me, you would be amazed who runs these operations. It is not just grand senators in silk. It is father and son partnerships working out of Baetica, small freedmen syndicates, former slaves who pooled their savings to buy olive groves and shipping contracts. They build massive family fortunes off guaranteed state oil supply contracts, leaving their family names stamped forever into the handles we throw onto the pile.

Marcus Valerius

I ended up buying a small, modest terra-cotta flask of oil directly from a merchant who was decanting a freshly inspected Spanish jar right on the quay. As I walked away from the roaring riverfront, carrying my little flask home for supper, I looked back one last time at the great brown hump of Monte Testaccio rising above the storehouses. It is strange to think about it. Rome's grand temples, its legions on the Danube, its million people eating dinner tonight, the whole glory of the empire relies on a mountain of discarded clay and black ink signatures on a dock riverfront. Well, that is the city for you. I will talk to you next time as we walk the streets of Rome.