Why Ancient Rome is Buried

I'm Garrett Ryan, and this is The Short Answer. Today's question is, Why is ancient Rome buried? As everyone knows, ancient Rome is deep underground. Take, for example, the Curia in the Forum, an ancient building converted into a church during Late Antiquity. By the Middle Ages, the ground level had risen so much that a new door had to be cut into the wall, 10 feet, or 3 meters, above the original. The ground continued to rise, and, during the Renaissance, another door had to be cut, this time more than 20 feet, or 6 meters, above the ancient pavement. The difference between ancient and later ground levels is equally obvious in the nearby temple of Antoninus and Faustina, where the door of the church that was built into the temple during the Renaissance is two stories above the ancient street. So where did all that soil come from? One humble but hard-working cause was wind-blown dust and weeds. In a temperate climate like Rome's, plants take root on the roofs and walls of untended buildings. If you look at a modern building that's been abandoned for a couple decades, like Detroit's Packard Plant, which is shown here, you can already see vegetation, and even full-sized trees, sprouting from every surface. Before they were cleaned in the 19th century, Rome's ruins had similar rooftop forests, as this painting of the Colosseum illustrates. The soil produced by the lives and deaths of these urban jungles built up slowly but steadily, perhaps an inch or a couple centimeters every century. Plants, however, accounted for only a small fraction of the rise in Rome's street level. Until the Tiber Embankments were constructed in the 19th century, Rome was prone to serious floods, which sometimes rose as high as 15 feet, or 5 meters, above street level in the vicinity of the Pantheon. When the water receded, it often left thick layers of silt. Built-up trash also contributed to the rise of Rome's streets. Far and away the greatest culprit, however, was debris from ruined buildings. In a typical Roman apartment building three or four stories tall, the outer walls were brick-faced concrete and the roof was tile. But almost all the rest was wood. Once the building was abandoned, all that wood decayed. And, once rain and frost weakened the mortar, and earthquakes brought the walls, crashing down, there would be a grass-covered mound, a story or so tall, on the site of that apartment building. In the case of a large structure, that mound might be the size of a small hill. The medieval inhabitants of Rome scavenged bits of stone from these piles, but they had no use for broken tile or hunks of concrete. So, they simply ignored the rubble, or leveled it and built on top of it. And that, my friends, is the short answer. Rome was buried by its own rubble and trash, by river mud, and by a little bit of dust in the wind. If you have a question about the Greeks and Romans that you'd like to have answered in a few minutes, please let me know in the comments. In the meantime, stay tuned for my longer videos, which publish on Fridays. And thanks for watching!